using blender 2.55 svn r32748 64 bit
built on kubuntu 10.04.1 64 bit
running on kubuntu 10.04.1 64 bit, 8 GB RAM, quadcore AMD Phenom
graphics card nvidia gtx460 based card ith 1gb ram

the fast gaussian node produces wrong results once a certain resolution in combination with high blur values is used. The image starts to get artifacts (vertical stripes and blocks) and its asymmetrical in regard to the x axis.

This seems to indicate some type of overflow in internal values.

The same bug is true for blender 2.49b

I have attached a blend file showing this effect.

steps to reproduce:

- open the blend file and press f12 to render it
- the output resolution is set to FullHD (1920x1080)
- close the render window
- you see in the compositor two tree branches setting up a vignette with a fast gaussian at the end
- one branch is using a 50% sized image and the produced result is correct
- the other branch uses the full resolution and here you see the incorrect results