Utorrent is what I use and I think I have the latest.

I haven't noticed any issues with mine of late though. Hrrrmm, Maybe whip up the task manager and see how much juice things are using when you crank it up? Perhaps something goes into overdrive.

I had that when I put daemon tools on my little laptop. After installing it, after boot up it would slow down, turns out since it was set (by default) to start up from the start up files, it was using about 50% of my little comp's resources.