When I run gimp and try to do the most basic operations (such as selecting a
section of an image and doing a crop to selection) it will hang X.  The system
will be unusable and the only way to regain control is to ssh in from another
system and run "killall -9 gimp" after which it will take a couple of minutes
to recover.  During that time Xorg will take 100% of one CPU core (the other
core being almost idle).

I tried running "ssh -Y localhost 'gimp file.jpg'" but that gave the same
result.  So even when X11 is tunneled over ssh it still gives the same result.

I've just done some more tests between the problem system (running Wheezy with
a kernel from Unstable) and the system that works well (everything from
Unstable).

If I run "ssh -Y wheezy gimp" from the Unstable system then everything is OK.
If I run "ssh -Y unstable gimp" from the Wheezy system then Xorg stops
working.

I think it's unlikely to be a Gimp bug as there are two different versions
(2.8.2-2 and 2.8.6-1) causing the same problems.

Also it should be noted that I have one of the worst bits of video hardware
that you are likely to see in an AMD64 system.  No-one who has a choice would
choose such a video controller, but the system in question is a Dell PowerEdge
server with PCIe*8 slots and it's almost impossible to find a matching video
card.