Hi there,
Every couple of days, my BB stops making sound for anything. The most irritating of which is the alarm because I want to rely on it . Vibrate works fine tho - and yes, a reboot usually does the trick. How can I stop this problem occurring? Do I need a software upgrade?
It sounds like the only permanent solution is to replace your device. As long as it's less than a year old, it should be covered under the phone's warranty.