Hi:
Welcome to ET!!
Sounds like you could be experiencing a pretty common problem with the headphone jack. It is a known weak point.
If you search the 650 boards for "headphone jack" you will find all kinds of info, some fixes, some work-arounds, suggestions, etc. Here is one to get you started:
http://www.everythingtreo.com/forum/...50-a-7902.html
Good luck and let us know how you make out. Do search around to make sure the jack problem is indeed waht you are experiencing.
SteveTaz