I just got back from Thailand, where my Unlocked Treo 650 would not log onto a network either automatically or manually. I have one SIM and it's an AT&T one I still use on Cingular. I'm running FW 1.71 SW, 120-ENA, and Hardware 'A'.

I had my iPAQ 6515 along and it logged on in Thailand just fine with a strong signal and GPRS using the same (my only) SIM.

Any thoughts?