Hy in made some strange experiences with grid fragments
looking a little bit like jpg grid.

This happens when I render a allready rendered video again.
I do this often when adding some little blur FX or Chroma
key to some previously cut video.
The more often i do rendering to the video material the
worser the fragments get. After the 4th or 5th time it is
getting rather obvious .....

Maybe this is a common Vegas Problem and there is a easy
workaround. It could also just be a codec problem (I use
the built in DV codec for rendering)

Thanx for any help .... OF