Ok I have searched for this and don't think it is the headphone jack issue some people have. I recently got a used treo 600. I had it added to my account yesterday and it worked fine until tonight. I used it at about 4:15 today and a few hours later no one I call or calls me and hear me. I can hear them fine but all they hear is a clicking and some static which I can hear also. I have tried a hard reset and it did not help. I first had the problem when trying to use a new body glove headset for the first time so I could be wrong and it may be the jack. It does not matter if I use the headset, speakerphone or regular.