I looked in ProcessExplorer and some .db files were opened by a hung cl.exe and cmd.exe process. Why would cl.exe have files in the VA vc8 directory open?
Visual Studio 2005, Windows XP x64 Edition, no other plugins
Happened again for 1533. I forgot to check if the files were locked before I ran the installer. This time it was only a cmd.exe that had the handles opened. I tried launching a cmd.exe from within devenv.exe (Tools->Visual Studio 2005 Command Prompt) and noticed that it had several handles from Visual Assist open. When I think about it it could be a Post Link event in my project that launch a cmd.exe. I have no idea why it would hang though. I think you could fix this problem if you don't open your file handles with the inherit flag set in the SECRURITY_ATTRIBUTES parameter to CreateFile.
This is the dump from Process Explorer of opened handles: