Normally I am good with customising SE phones, I have a 2nd hand k750 that had brown firmware turned red then converted to w800 (since I couldn't find brown w800 firmware).
Anyway, I also have a silver k800 that I updated foolishly with SEUS, and ever since this update, only T Mobile (or virgin, since they are the same network) sim cards will work in it. Any other card it will turn on fine but it will say "emergency calls only" or "inactive sim" and an icon with a cross thru a phone will appear. The phone was never locked as far as I am aware. Also, it has changed the CID of the phone to 53 (oh, *swears loudly*) so now only FAR Manager can access it. I have tried many firmwares for k800 CID53 (from SE Life .:. Life in SE! ) and no matter what firmware or FS I use (I know I am meant to use Europe 2 FS and the GENERIC MAIN as I am in England) it still says "inactive sim". When checking the simlock, all padlocks are open, so I know the phone isn't locked. It is not barred as T Mobile (or virgin) sim cards work in it fine. From various searches on the net I have stuck with the rule that the language customisation must match the CDA of the FS, but even this won't work... It may well be that this phone came from another country before it went on the market in my local area and they used custom firmware on it to get around the network restrictions. I noticed that it didn't say "k800i" on the 'phone status', it just said "Model: MODEL (yes that's right, capital letters) and every time I used XS++ when it was still CID52 it said "IMEI name doesn't match GDFS name. IMEI: k800 GDFS: MODEL". Now I can't use anything with it accept Far Manager of course... so...
to sum up, here's my question. Are there any modified firmwares for CID53 k800 phones to get around the "inactive sim" in the UK networks? Otherwise I guess I will have to take it back to the market and ask them to reflash it for me themselves, or wait a few months before CID53 becomes more supported, or switch from O2 to T Mobile. It's a shame, I love this phone :(