I posted a similar problem a few days ago:
http://forum.ppcgeeks.com/showthread.php?t=59178
Same EXACT problem, couple others with similar problems as well. What concerns me is that none of the senior members of this forum have posted anything. I don't know if there just not as active on these forums as they were when TP was new or what (most likely). Just very concerned that it is a hardware issue, not a software. Others have mentioend that reflashing fixed theirs, I am waiting some more feedback before I do anything. Have you flahsed your device to a new ROM or is it stock?