My blackberry curve will go through periods where I can't hear anything on it and no one I call can hear me. The call alerts still work but I am unable to hear the "say a command" prompt on the voice command. I have tried pushing the mute and the volume and nothing works. I am becoming more and more frustrated with this phone!
What have attempted to fix this? Have you tried the battery pull? If so, I assume that the "Mute" comes back? Do you accidentally mute the phone? Have you tried applying any updates that may exist for the phone?
If it is the 8330 I had the same problem.I corrected it by a software upgrade. Make sure you have the most up to date software for the phone http://vzw.smithmicro.com/blackberry/download.aspx?ct=personal
Just another quick fix you may try...sometimes, if you plug a pair of headphones in the plug on the device and then unplug it, it might start working. I have heard of the phone staying in the headphone mode with the headphones unplugged. Worth a quick try. The next fix I would try would be the suggestion made to upgrade the OS or to reload the current OS. Either way, back up your device before doing so. Word of caution if you upgrade your OS to VZW's latest...read the thread here in the forums about the problems with the latest 8330 OS upgrade.
I have the same problem w/ my Curve 8330. It happens only when I get a voice note mms message. After I open and listen to the "text", if I try to make a call, the person at the other end can not hear me. If they try to call, I can hear the phone ring, but they can't hear me. The voice note mms some how mutes the volume I guess. A battery pull usually does the trick to correct this, but I also found that after I hear the message, I delete it, then I open the video recorder, play a video from my playlist for about a second or two and then that unmutes the phone and I am able to make and recieve calls again as usual. I haven't upgraded the os yet, so I don't know if that will fix the problem.