Vista - Webroot's Spysweeper Hangs during sweep

I'm using Vista Home...just updated my Spysweeper to 5.8. While running a
sweep, it got stuck and wouldn't continue its process. I then canceled the
sweep...now it's hanging during the cancellation process!

So 2 questions:

1. What would cause the hang? Bad file? Bad upgrade?

2. Why won't the program stop? It's still saying 'cancel in progress' and
that was 2 hours ago! Should I just turn off my computer?

Thanks...sorry for being so naive!

A~