Hi, I know there are posts about this issue - but i can't find one using my soundcard!

I'm using Mk2 Traktor time code and every so often the pitch will become erratic and jump everywhere. Then when I try to re calibrate I get 'Unknown Medium' issues. I have done the following:

- Cleaned the time code with vinyl cleaner
- Used another 3 turntables and the same issue
- Set the weight on my stylus and anti-skating
- Installed latest sound card drivers Windows 7 6.0.3 SP1 (M-Audio Connectiv)

I am using a single time code setup on the following spec:
- Traktor Scratch Pro 2.5.0
- Windows 7 64-bit Home Premium SP1
- Intel Core i5-3317U CPU@1.7GHz
- Memory 4GB

Any ideas what the problem could be? thanks