Comment 122 for bug 355155

Well, after days of uninterrupted use, I finally got a system freeze in Xubuntu 9.04. For me, this seems to happen most often when I am quickly moving between various open windows. Like alcCapone, my mouse typically still moves when the freeze occurs. My keyboard does not respond to CTRL+ALT+F1 (so I can't get to a tty), or to CTRL+ALT+backspace (so I can't kill X that way), but it *does* respond to ALT+SysRq+REISUB (which ultimately kills all processes, syncs data to the hard drive, and reboots).

The fact that (1) this occurs on various kernels and various *buntus, and that (2) the mouse and keyboard remain responsive while commands to the X server receive no response (windows do not respond to clicks, the server doesn't let me move to a tty or restart it with CTRL+ALT+backspace, etc.), suggests to me that the problem I (and alcCapone, and others) are experiencing is a problem with the new X server (1.6.0). I'm going to see if downgrading the X server fixes things.

IN THE MEANTIME, if the above is right, then this all suggests that there MAY be a workaround available, which unfortunately I neglected to try last time: when the freeze occurs, try ALT+SysRq+K. Theoretically, this should kill the X server. If the problem is indeed something with X, then killing it this way should break us out of the freeze. alcCapone, can you try this if the problem occurs for you again? (I am going to try to force a freeze to occur and see if this works for me, too.)

@YS1: Did your freeze occur when you were using X (even if not using GNOME)? If not, then perhaps we're talking about different problems here.