On my HP Vectra VL6/266 Series 7DT with Cirrus card the XFree server can freeze up on random events, but quite often. One cannot switch to the console withc ctrl-alt-f1 etc. and cannot telnet to the machine to kill the X server. The reset button on the front of the machine does not work anymore! The only solution is to pull out the mains and plug them back. This problem is not there with XFree 4.
If the problem is not in XFree86 4, then it isn't considered a bug. Use XFree86 4.x and there should be no problem. We only use XFree86 3 for cards that do not work at all with 3.x.