Are you using Software Pageflipping to output the 3D movie to the 3D DLP projector?
Check the load of your processor when playing back the 3D movie, if it is fully loaded when decoding the video it just isn't capable of performing well enough, but if it is barely loaded, then there might be something wrong with the software. You can try using different codecs for decoding the video as the CPU you've got should be capable of performing decent with 3D video playback.
Alternatively you can also try other 3D video players such as:
sVideo - http://3dvision-blog.com/4981-sview-stereoscopic-3d-multimedia-player-version-11-03/
PowerDVD - http://3dvision-blog.com/7084-cyberlink-has-released-the-powerdvd-12-video-player-software/