audio distorts after rewinding in winamp and media player

Among other problems I am having, such as freezing up in win 7 for no reason, (often when the system is doing nothing-even in screensaver mode) I am having another problem. When using winamp or media player, if i rewind a few times (like 6 seconds back) the audio starts to distort. It never did this before. So far I have not noticed a problem when using my audio recording software (sonar). Which is odd because I run a lot of tracks and plug ins. What could this be? This system is on it's last legs but I find this rewind problem odd because I have always been able to do that even on much older systems without a problem
I am using a mackie onyx firewire for audio interface
I have recently added a vantec usb3 card