Computer bogs down running max 5 patcher on Lion machine

I hope someone might be able to help me. I'm using a video mixing patcher that I've used many times before and now I've run into this problem that I think may be Lion related. I have the last version of Max 5 installed on a macbook pro, 4gigs of ram. When I start the patcher it is working fine, mixing two video files no trouble but after a few minutes the computer seems to bog down. The frame rate on the video playback does not change but the laptop takes more and more time to respond to keyboard or mouse commands. It keeps running but I can't control anything. The patcher has not changed, the video clips have not changed, the only difference is the OS. When I look at the CPU monitor in Max it says 0%. Any ideas?
Thanks! --Erik