just did upgrade from k800i to k810i
with zero errors so far..
did with XS++

here are the logs...
20:27:57| XS++ v3.1 (Darwin) Ready !

20:27:57| Executed on Microsoft Windows XP

20:28:02|

20:28:02| Attempting to open the interface...

20:28:02|

20:28:02| TURN OFF PHONE!

20:28:02| Hold 'C' button on phone and connect phone NOW.

20:28:02| You have 30 seconds...

20:28:02|

20:28:33| Error: Cannot open phone communication port

20:28:35| Disconnected... Unplug the phone

20:28:37|

20:28:37| Attempting to open the interface...

20:28:37|

20:28:37| TURN OFF PHONE!

20:28:37| Hold 'C' button on phone and connect phone NOW.

20:28:37| You have 30 seconds...

20:28:37|

20:28:37| Baseband ID: 9900

20:28:37| Protocol Version: 3.1

20:28:37| Phone name detected!

20:28:37|

20:28:37| Profiling SEMC phone...

20:28:37| Platform: DB2020

20:28:37| OTP CID: 51

20:28:37| EROM CID: 52

20:28:37| EROM Color: Red

20:28:37| IMEI: 35570401xxxxxx

20:28:37| Phone ID: K800

20:28:37| Region: S_E_EUROPE

20:28:37| CDA: CDA102511/101 R1A

20:28:37| Firmware Version: R8BF003

20:28:37| EROM: R3A022

20:28:37| Ready for operation!

20:29:27| ~~~~~~~~~~ Custpack information ~~~~~~~~~~

20:29:27| Custpack: EUROPE_4 (CDA102511/101) (K800)

20:29:27| Generic(non-branded) custpack: Yes

20:29:27| Allowed languages: en, da, fi, is, sv, no,

20:29:27| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

20:29:36| ~~~~~~~~~~ Custpack information ~~~~~~~~~~

20:29:36| Custpack: EUROPE_5 (CDA102511/49) (K800)

20:29:36| Generic(non-branded) custpack: Yes

20:29:36| Allowed languages: en, fr, de, it,

20:29:36| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

20:29:41|

20:29:41| Sending db2020_cid01_prodid_p3j.bin...

20:29:41| Applet ID: 070129 0950 NGUCXC1250330_DB2020_PRODUCTIONIDLOADER_P3J

20:29:41| This is a PRODUCTION_ID loader

20:29:42|

20:29:42| Sending db2020_mem_patcher_cid52_r2a006.bin...

20:29:42| Applet ID: 061205 1523 HANCXC9876543210_DB2020_MEM_PATCHER_R2A006 0

20:29:42| This is a MEM_PATCHER loader

20:29:42|

20:29:42| Sending db2020_cid52red_flash_r2a005.bin...

20:29:42| Applet ID: 061201 1314 HANCXC1329129_DB2020_FLASHLOADER_R2A005

20:29:42| This is a FLASH loader

20:29:42| Now flashing firmware main...

20:29:43| Flashing c:\documents and settings\administrator\my documents\downloads\compressed\xs++\k810i\k810_r8b a024_main_generic_sm_red52.mbn

20:29:43| Header type: BABE

20:29:43| 460 flashblocks

20:33:31| Finishing flash

20:33:31| Done flashing

20:33:31| Now flashing filesystem...

20:33:32| Flashing c:\documents and settings\administrator\my documents\downloads\compressed\xs++\k810i\k810_r8b a024_fs_europe_5_red52.fbn

20:33:32| Header type: BABE

20:33:32| 213 flashblocks

20:35:17| Finishing flash

20:35:17| Done flashing

20:35:17|

20:35:17| Sending db2020_red52_cs_r3a009.bin...

20:35:19| Applet ID: 070410 1557 HANCXC1250562_DB2020_CSLOADER_R3A009

20:35:19| This is a CHIPSELECT loader

20:35:19| Activating loader...

20:35:19| Activating GDFS...

20:35:41| This loader is UNLOCKED

20:35:41| Success! CS-loader has been unlocked!

20:35:41| Uploading customization files to phone...

20:35:41| Uploading /tpa/preset/custom/CONTENT_DOWNLOAD_HOOK.itm...

20:35:41| Activating filesystem

20:35:49| Creating directory /tpa

20:35:49| Creating directory /tpa/preset

20:35:49| Creating directory /tpa/preset/custom

20:35:49| Deleting file /tpa/preset/custom/CONTENT_DOWNLOAD_HOOK.itm

20:35:49| Deleted...OK!

20:35:49| Uploading file /tpa/preset/custom/CONTENT_DOWNLOAD_HOOK.itm

20:35:49| Done uploading

20:35:49| Uploading /tpa/preset/custom/FM_PICTURES_HOOK_3.itm...

20:35:49| Creating directory /tpa

20:35:49| Creating directory /tpa/preset

20:35:49| Creating directory /tpa/preset/custom

20:35:49| Deleting file /tpa/preset/custom/FM_PICTURES_HOOK_3.itm

20:35:49| Deleted...OK!

20:35:49| Uploading file /tpa/preset/custom/FM_PICTURES_HOOK_3.itm

20:35:49| Done uploading

20:35:49| Uploading /tpa/preset/custom/FM_SOUNDS_HOOK_3.itm...

20:35:49| Creating directory /tpa

20:35:49| Creating directory /tpa/preset

20:35:49| Creating directory /tpa/preset/custom

20:35:49| Deleting file /tpa/preset/custom/FM_SOUNDS_HOOK_3.itm

20:35:49| Deleted...OK!

20:35:49| Uploading file /tpa/preset/custom/FM_SOUNDS_HOOK_3.itm

20:35:49| Done uploading

20:35:49| Uploading /tpa/preset/custom/FM_THEMES_HOOK_3.itm...

20:35:49| Creating directory /tpa

20:35:50| Creating directory /tpa/preset

20:35:50| Creating directory /tpa/preset/custom

20:35:50| Deleting file /tpa/preset/custom/FM_THEMES_HOOK_3.itm

20:35:50| Deleted...OK!

20:35:50| Uploading file /tpa/preset/custom/FM_THEMES_HOOK_3.itm

20:35:50| Done uploading

20:35:50| Uploading /tpa/preset/custom/FM_VIDEOS_HOOK_3.itm...

20:35:50| Creating directory /tpa

20:35:50| Creating directory /tpa/preset

20:35:50| Creating directory /tpa/preset/custom

20:35:50| Deleting file /tpa/preset/custom/FM_VIDEOS_HOOK_3.itm

20:35:50| Deleted...OK!

20:35:50| Uploading file /tpa/preset/custom/FM_VIDEOS_HOOK_3.itm

20:35:50| Done uploading

20:35:50| Uploading /tpa/preset/custom/GAMES_HOOK_3.itm...

20:35:50| Creating directory /tpa

20:35:50| Creating directory /tpa/preset

20:35:50| Creating directory /tpa/preset/custom

20:35:50| Deleting file /tpa/preset/custom/GAMES_HOOK_3.itm

20:35:50| Deleted...OK!

20:35:50| Uploading file /tpa/preset/custom/GAMES_HOOK_3.itm

20:35:50| Done uploading

20:35:50| Uploading /tpa/preset/custom/MEDIA_PLAYER_HOOK_3.itm...

20:35:50| Creating directory /tpa

20:35:51| Creating directory /tpa/preset

20:35:51| Creating directory /tpa/preset/custom

20:35:51| Deleting file /tpa/preset/custom/MEDIA_PLAYER_HOOK_3.itm

20:35:51| Deleted...OK!

20:35:51| Uploading file /tpa/preset/custom/MEDIA_PLAYER_HOOK_3.itm

20:35:51| Done uploading

20:35:51| Uploading /tpa/preset/custom/ORG_APPLICATIONS_HOOK_3.itm...

20:35:51| Creating directory /tpa

20:35:51| Creating directory /tpa/preset

20:35:51| Creating directory /tpa/preset/custom

20:35:51| Deleting file /tpa/preset/custom/ORG_APPLICATIONS_HOOK_3.itm

20:35:51| Deleted...OK!

20:35:51| Uploading file /tpa/preset/custom/ORG_APPLICATIONS_HOOK_3.itm

20:35:51| Done uploading

20:35:51| Uploading /tpa/preset/custom/SETT_RINGTONE_HOOK_1.itm...

20:35:51| Creating directory /tpa

20:35:51| Creating directory /tpa/preset

20:35:51| Creating directory /tpa/preset/custom

20:35:51| Deleting file /tpa/preset/custom/SETT_RINGTONE_HOOK_1.itm

20:35:51| Deleted...OK!

20:35:51| Uploading file /tpa/preset/custom/SETT_RINGTONE_HOOK_1.itm

20:35:51| Done uploading

20:35:51| Uploading /tpa/preset/custom/SETT_SCREENSAVER_HOOK_1.itm...

20:35:51| Creating directory /tpa

20:35:51| Creating directory /tpa/preset

20:35:51| Creating directory /tpa/preset/custom

20:35:51| Deleting file /tpa/preset/custom/SETT_SCREENSAVER_HOOK_1.itm

20:35:52| Deleted...OK!

20:35:52| Uploading file /tpa/preset/custom/SETT_SCREENSAVER_HOOK_1.itm

20:35:52| Done uploading

20:35:52| Uploading /tpa/preset/custom/SETT_STARTSHOW_HOOK_1.itm...

20:35:52| Creating directory /tpa

20:35:52| Creating directory /tpa/preset

20:35:52| Creating directory /tpa/preset/custom

20:35:52| Deleting file /tpa/preset/custom/SETT_STARTSHOW_HOOK_1.itm

20:35:52| Deleted...OK!

20:35:52| Uploading file /tpa/preset/custom/SETT_STARTSHOW_HOOK_1.itm

20:35:52| Done uploading

20:35:52| Uploading /tpa/preset/custom/SETT_WALLPAPER_HOOK_1.itm...

20:35:52| Creating directory /tpa

20:35:52| Creating directory /tpa/preset

20:35:52| Creating directory /tpa/preset/custom

20:35:52| Deleting file /tpa/preset/custom/SETT_WALLPAPER_HOOK_1.itm

20:35:52| Deleted...OK!

20:35:52| Uploading file /tpa/preset/custom/SETT_WALLPAPER_HOOK_1.itm

20:35:52| Done uploading

20:35:52| Uploading /tpa/preset/custom/VIDEO_PLAYER_HOOK_1.itm...

20:35:52| Creating directory /tpa

20:35:52| Creating directory /tpa/preset

20:35:52| Creating directory /tpa/preset/custom

20:35:52| Deleting file /tpa/preset/custom/VIDEO_PLAYER_HOOK_1.itm

20:35:52| Deleted...OK!

20:35:52| Uploading file /tpa/preset/custom/VIDEO_PLAYER_HOOK_1.itm

20:35:53| Done uploading

20:35:53| Uploading /tpa/preset/custom/Customize.xml...

20:35:53| Creating directory /tpa

20:35:53| Creating directory /tpa/preset

20:35:53| Creating directory /tpa/preset/custom

20:35:53| Deleting file /tpa/preset/custom/Customize.xml

20:35:53| Deleted...OK!

20:35:53| Uploading file /tpa/preset/custom/Customize.xml

20:35:53| Done uploading

20:35:53| Uploading /tpa/preset/custom/preloaded_config.xml...

20:35:53| Creating directory /tpa

20:35:53| Creating directory /tpa/preset

20:35:53| Creating directory /tpa/preset/custom

20:35:53| Deleting file /tpa/preset/custom/preloaded_config.xml

20:35:53| Deleted...OK!

20:35:53| Uploading file /tpa/preset/custom/preloaded_config.xml

20:35:54| Done uploading

20:35:54| Uploading /files_to_upload to phone...

20:35:54| Sending shutdown command to phone...

20:35:54| Customizing was SUCCESSFUL!

20:35:54| Disconnecting phone...

20:35:54| You may now unplug your phone.

20:35:54| Flashing was successful

20:35:56| Disconnected... Unplug the phone

21:00:57| Shutting down...