McAfee hangs computer

[issh1]

I recently re-installed windows XP Pro and installed the most recent version of McAfee that my college provides us with. On my previous installation everything ran fine, however, on the new installation whenever I start a program I noticed (from the task manager) that McAfee is eating up alot of CPU cycles. It takes a signficantly larger amount of time to start a program and some programs won't start at all, like Doom 3. When I disable on-access scanning, everything works fine. I don't really want to disable on-access scanning because from what I can tell, if I do, there is no point in even having the program running. I'm also running zonealarm if that helps at all. Any suggestions?