It's probably the unpacking engine at work. Unpacking archives (zip, rar,...) takes a lot of system resources.
I also have resource problems when playing "Call of duty" and "Wolfenstein"
and running the resident shield in the same time.
It's because (my situation) these games have (consist) of many large archives.
My pc is a PIII 1ghz, XP, 384 mbram.
I simply shutdown (temporarily) the resident shield when playing these games.
Waldo