On Sprint, it doesn't support US SIM cards. There's a bit of code in the radio that doesn't allow US network codes to connect. There's a bit of reading on it from the elite team around here on the forums - though I hate how they are just generally vague and don't really share what they're doing.

http://forum.ppcgeeks.com/showthread.php?t=93865

And yes, it was your .erv. I was wondering why you left out OSModules?