Palm has just issued an update for the Treo 750 smartphone. The Treo 750 can “enter a state where sounds are lost for phone calls and notifications.” This update fixes the issue. Palm does note that the update is erased in a hard reset, so you will need to install it again if you ever clear storage on the device.
Treo 750 Smartphone Audio Alerts Update
Buy a Treo 750 from LetsTalk.com ($149.99 with New Service)