My phone has that same sim card problem as well. It will display a small picture of a sim card with a red slash across next to the battery icon. When it used to do it, it would be several times a day but then it would re-register automatically and get back online with T-Mobile. So I didn't really let it bother me too much since it would always be back online within a few minutes. Now it's been happening a lot more and it never comes back online anymore. I'm always having to power off my device and power it back on in order to have the sim card work properly and NOW this is really starting to piss me off! Sometimes the power on even fails where it doesn't reach that screen with the two holding hands and just shuts off again while it was on the startup screen with the 4 scrolling dots. This is the point where only a battery pull will work and THAT is starting to piss me off as well. I never bothered to research on doing a flash cos I never needed to but now I'm thinking it's inevitable. My wife's N900 works flawlessly (knock on wood). If I do a flash, will I have to setup all of my contacts and merge them into conversations app and everything? Gee I'm hoping the firmware update that's coming out soon will rectify this problem.