Sprint's Motorola Photon 4G is in the midst of a little bugfix update this week. You can either go into the settings menu and start the update that way, or just wait for the update notification to appear.
Here's what's being fixed in software version 4.5.1A-1_SUN-154_5:
Improvements to voice calling to eliminate inadvertent voice calls defaulting to mute
Improve stability, resulting in fewer occurrences of unresponsiveness
Bluetooth support for mono headsets with the Sprint Visual Voicemail application
Yeah. Muted calls are a big one, as is stability. Good on Sprint and Moto for getting that one pushed out soonest.