ATI pbuffer slowdown

Hi all;
Im doing a glow fx using pbuffers, and in NVIDIA hw no problems, but in ATI the fps goes down from 60 to 0.05 …im doing this way:

before loading any texture:

  1. Create a pbuffer_blur 256x256
  2. Create a pbuffer_glow 256x256
  3. Initialize the VBOs and other texures
  4. Render everything to pbuffer_glow, with tex env set to rgb*alpha
  5. Bind pbuffer_glow (as texture_2d) and render it with radial blur to pbuffer_blur
  6. Render the scene
  7. Draw a quad over the whole screen with pbuffer_blur

Im clearing only the depth_buffer_bit of the pbuffer_glow (im rendering a black retangle on the viewport to clear it), and the slowdown is on the step 7…using Visual Studio and debugging, pressing ctrl-f10 (to go to next instruction) last about 3 seconds just for the glEnd() command of the quad rendering…is something wrong with the order oc pbuffer creation, or size of them?

Hi !

I think the advanced forum would be better place for this subject…