fglrx-driver doesn't work with stock kernel

[Jerry <j3rry1337@googlemail.com>]

Hi there.

I recently reinstalled Debian stable, and one of the first things I did
was to install the fglrx-driver:

sudo apt-get -t squeeze-backports install fglrx-driver fglrx-control
sudo aticonfig --initial

After a reboot, I could use my display's native resolution (which was
not possible before). However, it seems to me that neither 2D nor 3D
acceleration is working with the stock kernel (i.e. 2.6.32-5-amd64).

glxinfo produces an error:

X Error of failed request:  BadRequest (invalid request code or no such
operation)
  Major opcode of failed request:  136 (GLX)
  Minor opcode of failed request:  19 (X_GLXQueryServerString)
  Serial number of failed request:  18
  Current serial number in output stream:  18

Then I tried the linux kernel from the backports (i.e.
3.2.0-0.bpo.2-amd64), and it worked. I could run glxinfo, glxgears and
play games. (However, from time to time a white 1 on a red background
appears. I can get rid of it in the Catalyst Control Center (it's the
number that is used to identify displays), but as I said, it just
randomly appears. Weird.)

FYI, I'm using a AMD Radeon HD 6850 graphics board.

So, um... any ideas on what the problem might be? I mean, I have already
used fglrx-driver from backports with the stock kernel, so I don't quite
understand why it's not working right now.

Jerry