I couple of months ago I posted here about how a crash to one of my Cydia apps caused me to have to rejailbreak my phone and after that and the ultrasn0w unlock, the phone wouldn't recognize my SIM card. I tried everything...got a new SIM from TMobile. Re-did the jailbreak using redsn0w, JailbreakMe.com and PwnageTool. My friend's AT&T SIM cards worked and so did a friend's TMobile SIM, but not mine. Well last night I did the update to 4.1 and the jailbreak using PwnageTool. Unlocked it again. Still nothing. Pop in my SIM and nothing happens. Even after a reboot. Today, on a lark, I borrowed my friend's iPhone and put her AT&T SIM in it. Worked great. Put my TMobile SIM in her phone and hers at least sees my SIM and says "Invalid SIM." I mucked around looking at a few settings but didn't change anything, then switched them back. For the first time, instead of the No SIM message, it went to "No Service" then a few seconds later the bars appear, then TMobile! I've made some calls and texts. It works great again. What do you suppose happened here? Was putting a legit SIM in the phone after the software update something that might have triggered it or what?