Are you running the Sprint roms of 2.1 (leak or official)? If so, the process to mount the phone is a bit different than it was in 1.5, HTC sync will no longer automatically pick up the phone and vice versa. You have to manually switch it into HTC sync mode on the phone. In the notification bar you will see the USB symbol. Pull down the notification bar, and it will probably say "Charge Only" Select "HTC Sync" and then hit "Done". Now HTC Sync and the phone should see each other. Once again, I can only speak for 2.1 roms from Sprint, (Leaks and Official) I hope this works for you.