Live/tracktion Cpu Utilization Weirdness, they run better if Virex is running too! Options

[guatamaham]

ok. so I was running a virus scan on my disk after a reboot (just a normal procedure for me since I seldom reboot anyway :-)) and I'd just downloaded the Reaktor demo so I wanted to check it out. I threw in some sequence clips and started throwing in Reaktor instances. I know it's heavy on the CPU so to my surprise, I could get 4 instances of Reaktor to run. BUT when I turned the virus scan off, the CPU meter in Live shot up to 120% and audio started to crackle like hell. then I could only get two instances to run before audio crackled from CPU overload.

I tried the same thing in Tracktion, which is a new "baby" sequencer costing 1/5 of what Live does; it could run 6 instances of Reaktor with room to spare (which should go to show you that Live 4 could use a little fine-tuning in the efficiency department). but when I turned Virex off, it did the same as Live - CPU overload and I had to delete two Reaktors to get it to run right.

I did more tests including using different VSTi's in each program and running a Live set where everything was bounced to audio clips and only a couple effects (no instruments) were being run. they all exhibited the same behaviour.

anyone know what gives? is this a Mac thing only (I'm running a 1.33Ghz Pbook w/1.25GB of RAM under OS X)? should I just scan my disk every time I run Live now? is there some Mac optimization that I should be doing that would account for this weirdness?

thanks in advance!