The shader used for TF doesn’t need to know about the existence of TF. It just writes to the output varyings.
Damn, I’m trying the way ‘yooyo’ suggested…
This ATI driver drives me crazy (9.5 at least). The error InvalidOperation is generated on BindBuffer(PixelUnpackBuffer,0) call…
Common, PBO was introduced in 2007. Is it so difficult to get it work after 2 years on ATI?..
BTW, I’ve filed a support request on the AMD developer central about TF issue. Still no answer. AMD seems not care much about developers, doesn’t it?..
Have you tried whether the bug is still there in the 9.8 driver (that is the newest one)? There is not really a point in sending a bug report for an old driver I guess, unless you know the bug is still there in the newest driver.
I sent a bug report a while ago, together with sample code and system details. I got a great response that said they couldn’t reproduce the bug with the newest drivers and asked whether I could verify if the bug was gone with the newest drivers. It was gone indeed, so I was satisfied.
Lucky you, Heiko!
With a bug file about TransformFeedback I attached the simple C source (using GLew & GLFW) that reproduces it. I specified that it crashes on both 9.5 and 9.8. If there was something they need to know in addition, why not ask me?..
BTW, did you use AMD dev central support system? How have you posted a bug so that they noticed it? 
I emailed everything to devrel[at]amd.com. System details were gpu, cpu, motherboard, amount of memory, OS and the driver I used. The code was a minimal example, well documented, not using any external libraries.
Thanks, Heiko.
I’ve mailed them just now as well. Provided detailed SysInfo output. Hope to get some answer…
Finally!
After some pure discussion with different AMD departments, I’ve got an advice to try 9.9 and check if the bug is still there (yes, they admitted it to be a bug).
Surprisingly, TF works in 9.9 under my GL-3.0 forward-compatible context. Congratulations for everyone who were waiting for this event!