I also have the same problem with an HTC TYTN II. The phone is less than two months old and had it sent for diagnostics at HTC. Their reply was $367.78 for a mother board replacement. They are alleging that the problem is "customer induced". In other words, I damaged the USB port however; how can one damage a USB port if the only accessories used were provided by HTC? (A/C and PC charger)
I have always been attracted by HTC products. I myself still own an MDA and was much exited with my brand new TYTN but, that has changed after my conversations with their various representatives. No one really cares, they just go by the notes they see on their screens and there is no turn around. No supervisor to talk to or no solution to your problem. To make things worse, one pays for shipping and insurance the first time and then, if the customer does not agree to the charges, a $35.00 diagnostic fee is charged to your credit card.