Utorrent freezing computer?

[Schizophonic]

I didn't experience this before a rebuild recently but when ever utorrent is launched and I add a download - it freezes my PC and doesn't stop it completely. I move the mouse around the screen and it picks up again. Now the freeze can be as long as 5sec to 1min.

I couldn't find a direct solution so I'm using Vuze (what was Azureus)

Anyone else encounter this problerm?