Help SIM sometimes not recognized after unlock


A few days ago I rooted and unlocked my new Samsung Infuse 4G using a method I found on xda-developers. At first, everything worked just fine, but the next day it couldn't find the network (I'm on T-mobile) and when I go to Settings -> Wireless and Network -> Mobile networks, a message pops up saying "Insert SIM card to access network services". A while later, the network came back and everything worked fine. Then it stopped working and it's been going back and forth unpredictably. A similar thing happened on my previous Android phone (Star A7000) for the first few days after unlocking it, but I don't know if this is going to stabilize on the Infuse. Did this happen to anyone else?