Do you keep this on or off while running games and why?
In the past I have always kept it turned off because it interfered with my PunkBuster settings and I kept getting kicked and experiencing bad lag. Wondering if it was just that game or everyone keeps it off now?
I always disable real time scanning when in games, its gives me necessarily long load times and in game lag.
Just make sure its up-to-date and you run scheduled scans, eg, when i am at work once a month i do a scan.
I also find its useful to reinstall MSE every now and again as its seems to get very resource hungry the older it gets.