I am seeing the same issue in a current install I am doing for a customer. From what we can tell through process explorer the Symantec AV client has the mfc71.dll file locked. If we shut down the symantec AV services that file is freed up, but we still have msvcp71.dll and vsvcr71.dll locked. Shutting down all the process below and closing all explorer windows freed up all the files mentioned.
Services we stopped:
SAVROAM.exe
Symantec Antivirus
Syamntec definition watcher
Syamntec event manager
Syamntec settings manager
Hope this works for you.
-Cheers