problems with unlock 2g

the iphone works fine without a sim in it, and accepts the sim (im using h20 ) but a few minutes into a phone call the phone glitches and drops the call, then come up with a call failed image and resets the phone. when i redo the jailbreak, bootneuter goes by in auto mode, even though ive restored to factory 3.1.2. have a feeeling that i screwed up the bootloader or baseband. i can still use wifi, is there anything to repair the baseband or bootloader, or whatever i need to repair to have the sim not crash the phone? the phone works with the sim only if i have airplane mode on.

 

is there any way to check? a utility for checkin the status?