UPSIDE DOWN BLUE frames on rendering many vid effects

I'm in DIRE need of help!! I've got a project with multiple video effects (like mosaic, find edges, solarize, etc) that significantly distort the video (in addition to Brightness, Color Correction effects). At first, clips rendered fine, but now whenever I render a sequence, random frames in almost every clip in the sequence will be rendered upside down with a dark blue tint over the image, or with heavy grey 'static' obscuring the entire frame, or (less frequently) pieces of two different frames from a totally different clip. Sometimes entire clips would render out like this.

One solution I found was to isolate the bad frames (ie, cut the clip up) and re-render them with slight changes in the effects (ex: adjust 'integrate with video' option +/- 1%), until the render finally worked. Besides being very time consuming, this method seems to no longer work. Any idea what is going on, and how I can render without these headaches??

I'm running PPro 2.0 on P4 3.2GHz, 2GB RAM, project files on 500GB ext hard drive.