Never seen this one before. If I peer real carefully at my latest video there's a permanent pattern of extremey faint gridlines over it. It only appears where there is extreme contrast, and only on the H264 based .3gp HD files rendered. The grid, off the top of my head, is about 25 across and maybe 10 up.

It appears most visibly on my white text on black background titles, but it's certainly there throughout.

Odd. Anybody seen this before?