I just checked the W850_R1ED001_MAIN_GENERIC_CY_RED52.mbn MAIN, and IT IS CORRUPTED. So my tool is working just fine, and XS++ confirms that:
04:51:30| Flashing e:\documents and settings\administrator\desktop\w850_r1ed001_main_g eneric_cy_red52.mbn
04:51:30| Header type: BABE
04:51:30| 455 flashblocks
04:52:46| Binary acknowledge failed with: 15
04:52:46| Failed
You no need to play with GDFS, etc. just download another version of MAIN (e.g. W850_R1KG001_MAIN_GENERIC_CY_RED52.mbn) an flash it. Your phone should work then...