I switched to Cingular, a GSM provider, so that I could roam internationally. I didn't realize, however, that I had to give up nationwide service. But, yes, it's true and now confirmed to me by Cingular technical support that there is a deep network bug that commonly blocks outgoing calls if international roaming is enabled when using the Cingular network outside of the home area.

In my two months with Cingular, my Seattle-based Treo 650 has worked in Paris, Amsterdam, and Budapest -- every international city I've tried. That's the good news.

The bad news, however, is that it has not allowed outgoing calls in a single of the American cities (Los Angeles, San Francisco on two different trips, and Detroit) that I've visited. Different problems in different cities. In San Francisco, all outgoing calls were directed to a non-working Cingular helpline. In Detroit, voicemail didn't work. In Los Angeles, it worked for about an hour, then I was greeted with a message saying that my service had been disconnected for nonpayment of my bill.

In each case, I was able to get service restored by calling from another phone (albeit after speaking with multiple customer reps and waiting upwards of two days). Yet, with each new trip the phone fails.

To their credit, a Cingular rep did follow-up and call me after the latest episode and explained that Cingular knows about this bug and has reset my connections in a way that they assure me will keep this from happening again. I've heard that before, but maybe the fifth time will be a charm.