[John Clark]

The only other thing I can think of is a similar problem I had with a pearl a while back. It had a radio problem on the 850Mhz band of the phone. Basically it worked fine with a TMobile sim card (1900Mhz) but when I placed another sim card from Unicel (it was unlocked) in it that used the 850Mhz band, the phone didn't work so good, and I got lots of call failed and no data. I finally had to return the phone to TMo for exchange. They sent me a new (refurb) one and all was fine after that.

It's possible that you have a defective phone that works on some radio frequencies but not others, as I did. One thing that I noticed on the problem phone was the signal arrows going back and forth were small and erratic as opposed to the larger normal arrows indicating data transfer.