MP3s cause QuickTime to crash - how do I reinstall QuickTime on Mountain Lion?
I know you "don't want to reinstall OS X," but the easiest way to reinstall Quicktime (the current version, which is not a standalone download) is to reinstall Mountain Lion via Recovery Mode. Following the introduction of Lion, Quicktime became apart of the OS X installation package. There is no need to take a roundabout method. Reinstallation using recovery is non-destructive and only reinstalls OS X builtin applications and system components.