I haven't seen this problem here so I was wondering if this happen to anyone else? I have a nextel 7520 with plantronics 640. They work fine together most of the time but for no apparent reason the vioce transfer from the 7520 stops working in mid DC or phone call. The only fix is pull the battery and reboot. This happened with my HS820 also, thats how I wound up with the plantronics (I thought the HS820 had died)