Quicktime stutter and lack of sound

I just installed MPlayer and VLC to view some files and now, when I try to use Quicktime there is a stutter every few seconds and no sound. The files I'm using are files that definatley have sound (they worked earlier today) and you can see the bars in the bottom right moving, but no sound. Sound dosen't work on streamed media via Safari either.I had this previously on my iMac and I reinstalled the OS and this solved it.
Does it have anything to do with VLC or MPlayer? Any ideas on how to solve it?

 

Found it...Apps/Utilities/Audio MIDI Setup change the sound frequency down. Weird how it just effected MPG's though.