I understand the Verizon rep told you that, but I'm skeptical.
If this were a device issue, it would need to be a fundamental database implementation problem on the device. This would end up effecting all users.
Now if it's a issue with the sync software and a certain combination of events or hardware (read PC) configs. then it could happen to the small percentage of users. I might be wrong, but this is totally where I would look...