I've also run across some weird things when rendering animations with the camera flying along a path. I would sugest 2 things: Set-up your flythrough as a bunch of keyframes instead and see what happens. It takes more work tweaking the keys, but I think it is more relyable. And, rendering out as an image sequence, (like pixelicious said.) Then you can see exactly where the weirdness is. You may also find that it goes away! I have had some strange things happen when rendered as an animation that disapeared when rendered to an image sequence. It's also safer if anything happens with your computer during the render. An animation can be corrupted if C crashes, but an image sequence is good up to the frame that crashes, AND you get the bonus of knowing what frame screwed up! :>