I am currently in St. Lucia and bought my N900 last year in December and it has been working fine since up until a two weeks ago. I am now having the same connection issues as most people in this thread and after some troubleshooting here are my findings:

1. It's not a problem with the network. All the phones in my house don't seem to have problems connecting to the cellular network. Most of them have full signal strength and my N900 doesn't even show the bar.

2. I get signal strength only when i leave my house and i used to get full signal strength at my house before. I don't understand it.

3. Tried securing simcard at the back and that didn't work either.

3. Deleted all applications, cleaned out device and reset to factory settings and still it doesn't work.

4. I can't re-flash the device as my micro-usb port popped out a couple of months ago. I can't send it to nokia either as i Overclocked the phone and spoilt my warrenty.

5. Toggling the offline mode doesn't work either. I don't know what to do....please HELP!!!!!