CHanging resolutions on a SDVO-DVI or SDVO-VGA pipe results in a Xserver crash on Sandybridge system.
Sounds very interesting. Please provide an Xorg.log, and a drm.debug=0xe dmesg. And if you can a full Xorg bt (either using the -core option and gdb on the corefile or by attaching to X with gdb at runtime).
With no more information, there is nothing we can do.