I had the "no sim card" problem last week, my n900 was working great, but i wanted to flash and start fresh, what happend was i flashed my n900 that was running PR 1.1 with the earlyer firmware then i got the sim problem, then i flashed with the PR 1.1 global and everything was fine again (phewww), no sim probs etc , i did however sh*t myself at the time lol, thought id ruined my n900.