Whenever I update an addon (version 3.0.0.9), it is very slow during the Extracting phase.  It just sits at about 50% for a long time (like 2-4 minutes), then it starts moving again.  Any ideas what may cause this?  I have Windows Vista.

Did you check free space on your drive? 

I have gigs free on my hard drive, so it can't be a space issue.

Upgrade to v4 of the client (link in the premium forums).  It's substantially more optimized.