Thought I would post this because it's odd and it may help someone.

Last month, I drained my n900 original battery (BL-5J) to the point where there was insufficient power to boot into charge-mode. I went out to find a replacement. The only battery I found was from a company called Winner Group (WG) with a battery claiming compatibility with the Nokia 5800, n900 and others. It worked for about 2 weeks ... then my SIM card began behaving strangely ... dropped by the phone frequently. The SIM was 2 years old so I replaced it. Worked for a day then the new SIM started getting dropped.

Now I had to decide if this was a hardware or software fault. Software is easy so I re-flashed my n900 with both vanilla and rootfs ... the SIM card was still dropped. My assumption was that this meant hardware and I was not happy. On a lark, I got a charging cradle for the original Nokia BL-5J battery. I charged Nokia BL-5J ... installed the charged battery ... the phone has been working fine for several days now.

So ... if you have switched to a non-Nokia replacement battery and experienced problems with your SIM ... try a Nokia battery. I can't explain it and it doesn't make me happy (in theory the Winner Group battery would last longer) ... but this seems to be the case.

Hope this helps someone else. Cheers.

i had the same problem when I got my mugen battery, just had to bend the contacts on the battery in tighter and it was fine after that.

I guess the SIM slot is very dependent on even more constant power than the device and os itself.

I'll try that. No point in wasting a battery. Thanks!

Check the shape of the battery. Does it seem fatter or bulging compared to the original? Thicker?