I just helped some fellow UNSW students fix Linux hanging when performing a graphical login (no, even the magic sysrq keys I enabled did not help). They were running X.org 6.8.2 (Fedora Core 4) with an ATI X600 graphics card (Dell Optiplex GX620).
I solved this by switching from the buggy opensource
radeondriver to the generic VESA driver i.e. in
Section "Device", I changed:
There are also 2 other solutions that apparently work:
1. Richard Zach suggests using the binary ATI driver.
2. Those students found that the opensource
radeondriver worked if they updated to X.org X11R7 (Fedora Core 5) [*]. Unfortunately, they need to run some closed-source software that only supports Fedora Core 4. Furthermore, this upgrade does not seem to help with an ATI X200, which experiences similar lockups.
[*] Does anyone know the exact version X.org number?