My only real frustration when using Linux is a fault that seems only to happen on some boxes and not others, and only when using GLX/3D acceleration, especially on nVidia but also occasionally on ATi.
What happens is that everything freezes except the mouse pointer which moves around the screen but its cursor stays fixed. Apparently if the computer is on a network, you can SSH into it (whatever that means) and find that X has taken over all your memory, you can close X and the computer is still running. Otherwise you are forced to press ALT-SYSRQ-S to save all open files, ALT-SYSRQ-U to unmount them and reopen them as read-only, and ALT-SYSRQ-B to reboot. There are other combinations that restart the keyboard, etc, but ultimately you never get up and running properly unless you reboot.
There are several theories about the origin of this fault. One is the nVidia drivers. I'm not sure about this, because I have read that it can happen in any 3D-enabled X setup. Another is the kernel. Another is somewhere in X.
Everyone blames the other, and you only read about it on forums. It never seems to be discussed in magazines, or acknowledged by any developers. At the nvidia help site, it is one of the biggest topics, but no "official" answers at all.
It also seems to strike randomly, I didn't have this problem for ages, and then it got so bad that I had to switch to the nv (2D) driver which is slow even in 2D.
It can strike in any distro, and there is no rhyme or reason. Two people with identical computers and identical distros can find that one persion never sees this bug and another sees it all the time. A little tweak of xorg.conf can result in it going away for a while only for it to come back with a vengeance later.
If developers can't work out what's causing it, can they at least add a means of escaping from it without having to reboot? Has anyone else had this problem?