I have the same issue. Can you please point me in the right direction as which pins you are talking about exactly? Maybe use the following picture:

http://www.google.com/imgres?imgurl=...0&tx=144&ty=56
Thank you.

You can't go by that pic, you will need to disassemble your N900 to be able to carry out the 'fix'. The antenna connectors are inside the device, underneath what you see in the pic.

Yes i know that. I did disassemble it. It is just a matter of which pins I should be looking at since there are more than just 2.
Can you maybe point them out to me using this video?
http://www.youtube.com/watch?v=aVEHm325-z8

Thank you!

That vid doesn't help. Have a look at the attached pic.

2 pins in red box and 1 pin in yellow box: bend all 3 slightly upwards away from the circuit board, they should then make better contact with their corresponding pads on the antenna module.

Just checked the Service Manual and it specifically mentions this procedure so you should adjust all 3 contacts; the 2 together are grounds, the one on its own is the feed. Hope this helps solve your prob.

This did not work for me, but thanks for the instructions. By the way, when my phone started doing this (sometimes it says "unable to connect to network. Contact service") on startup, and others the "all telephony...." message, but what I tried was changing batteries. At the time i was using an extended battery, so I went back to the OEM battery, and neither messages appeared again, and the phone was reading the SIM fine. Then a few weeks later, it started going on and off, meaning it would be connected fine and I would have strong signal, and then it would lose it and give me the no SIM symbol/ display a message. A few days later, it kept giving that message/ not reading the SIM. Today I tried this method, it still comes up with the "telephony" message. I have tried flashing it using multiple other files (many times), PR 1.3 mostly, I have changed my SIM, my carrier is T-mobile. Any other ideas? Thanks!

It would probably void your warranty if Nokia knew that you had disassembled your device: but as there are no seals to be broken, provided you made a neat job of whatever you're 'fixing' I can't see how they would know it had been apart... unless you left jam butty fingerprints all over the internals

Try a cotton bud dipped in alcohol/lighter fuel, rub it gently over the uppermost rounded prongs of the SIM card contacts, give it 5 mins to dry and reinsert your SIM. Also check that all 6 of the prongs are raised the same amount, you may find one that has somehow got pushed lower than the rest. It's worked for me with other devices in the past...

I got this problem about a week ago, it started intermittently but now it never reads any sim I try.
I also lost IMEI number for a while, actually at first even the word IMEI disappeared, then that came back with no number, and finally I have both again.
AND my App Manager screwed up so I couldn't download or uninstall any apps, but I fixed this by disabling all the catalogues and rebooting.

I only got the phone around 3-4 weeks ago from an Amazon seller so I emailled him first, and he recommended flashing using NSU. I couldn't do that because it won't work in offline mode, and the phone won't read my sim card.

So I flashed eMMC and firmware using "flasher-3.5.exe", was a lot easier than I thought and it seemed to work fine. But I still get the error message and still won't read my sim

The strange thing is, at first I had the sim icon with red line through it all the time... but now (since BEFORE the re-flash) I don't get that icon when there's a sim in the phone. But I still always get the error message and the phone doesn't ask for my sim PIN when it boots up.

Does it sound like dumpystig's contact-bending method would work for me? Why wouldn't the phone ask for the sim card's pin number, even if it can't connect to its GSM antenna?

This isn't IMO related to antennas.