I had this issue initially as well (have 7 x64 too). I’m not entirely sure what cured it though as I did a number of things and suddenly noticed it had stopped freezing. I’ll list the things I did in the hope that one of them is a cure for your problem too.

1. Increased cache size to 60%, as I noticed on occasions the picture would screw up and become a jumbled mess (similar to digital tv reception in stormy weather) and once cleared would be out of sync with the audio. I thought perhaps instead of giving me a scrambled picture when the cache wasn’t being filled quick enough it was crashing instead.

2. I don’t use a username or password for network shares, but on setting it up for the first time I entered a username (my own) and just left the password blank. Removed the username part later and just had them both blank (yah never know).

3. Stopped my Squeezebox Server from running. I doubt this did anything, but just to be on the safe side.

4. Switched everything off, Wii, PC, router, then proceeded to turn them back on starting with the router. This seemed to improve buffering speed, so that was a welcomed improvement.