**System Information**
Operating system and graphics card
Ubuntu 12.04 64bit
Nvidia 560Ti driver 304.116
**Blender Version**
Broken: 2.69.11 10f4c62
**Short description of error**
Combination
keying > scale (render size, offset) > alpha over
introduces missing chunks in preview image. Rendered image is fine.
If offset is changed from zero missing chunks are shown. Missing chunks are at random, and chunks size effects the shape and amount of "holes".
{F78918}