I've jailbroken my iPhone a bunch of times, each with no real problem. I recently upgraded to 3.0, didn't care for the bugginess, and downgraded back to 2.2.1. Now, after this last j/b, I have no signal, no carrier, etc. I reset the network settings twice to no avail. I tried restoring to factory settings, but iTunes wont let me. I had to re-jailbreak it just to get it to work at all. Please, anyone with any good suggestions?