This may not be the exact problem, but it may help a few people either way...

I had an issue with my n900 that was solved here regarding my signal dropping intermittently. If you take off the back panel (phone face down), the plastic panel to the left houses the aerial. If you take that off, underneath is two little prongs. You can bend these upwards a little fairly safely and replace the aerial.

In my case, the aerial wasn't secured down properly. Solution for me was to place a small piece of blu-tac underneath the top left corner of the battery cover to ensure extra pressure was being applied to the aerial and the connectors underneath.

Sorry if I've missed the point - I haven't read the whole thread, just the last few posts which talked about pressure being applied, and it was this same pressure that actually fixed the signal issues for me when the signal was dropping intermittently.

Happy Christmas, S