After a bit of hardware swapping in the house, I've ended up using an old Dell Dimension 3100 as my browsing/mail reading machine.
And so far the experience with Debian Testing has not been nice. The X server crashes
under minimal provocation. In particular, mythfrontend causes it to fail by
just breathing on it.
After some digging, I've updated my kernel to the latest 2.6.37 from the Debian experimental repository.
So far it's looking good. Changing Myth rendering from Qt to OpenGL and back was a reliable way of crashing X. It now survives, so fingers crossed….
(Two weeks later…)
Yes, that did the trick. No more X crashes since the upgrade.
Notice that you now have to use kernel modesetting to use the Intel X driver.
(Update 23/4/2011)
Bugger. After a recent update, it's broken again. Regardless of the kernel (2.3.27, 2.3.28), and Xorg driver, I now get kernel panics after a variable amount of X server usage. I've had to drop back to VESA. I've not yet managed to triangulate the offending change.
(Update 6/5/2011)
This looks like a kernel, or possibly hardware problem. The machine in question is a vintage P4. Turning off HyperThreading in the BIOS solves the problem, and I'm back to using the Intel driver. So, wobbly windows again, plus the occasional tendency to corrupt bits of display that aren't being refreshed.