[PROBLEM]
I've encoded a quite problematic scene using VirtualDub+AviSynth, so I could get a 50fps video (due to interlaced source), BUT the outcome was a completely scrambled mess of psychadelic colored blocks - and the whole image was upside down.
[SOLUTION]
Verify that you haven't tried to to a 3:2 pulldown removal in VirtualDub:
In "Video > Frame Rate > Inverse Telecine" choose "None (progressive)".
That should fix it.
(I'd like to attach a screenshot of the messed up video, but my player currently won't let me... strange, strange...)
xvid: psychadelic colors and image upside down
That's what it looks like...
Here's a screenshot of the broken video:
"....Lucy in the sky with diamonds...."
"....Lucy in the sky with diamonds...."