Sorry, I don't know why the BFU would be freezing. Try updating your AV, scan your computer & then try with the BFU again if necessary. if you don't have an AV program, these three are all free.
avast!

AVG free

Avira Antivir

Or there are links to online scans within this thread.
WARNING: Viruses on network you should be aware of!
Otherwise, go to one of those help sites that I mentioned in my first post