Something is broken

Something recently broke with the setup on my laptop.

Symptoms: when I switch from one application to another, suddenly nothing gets updated anymore. I can move my mouse around; but apart from that, the screen shows no updates. Judging by the sound of the fan, it would appear that something or other is looping at that point, too.

So far this has only happened when switching from one GTK+ application to another, but I haven't had enough of them to be sure it really is GTK+-related.

For reference, I'm using the best window manager out there, using the nv X.Org driver, and for now I've seen the lockups when switching between Liferea, Firefox, and Pidgin.

Of course, having a system lock up completely makes it rather hard to debug, especially if you're on the road and don't have a second system handy; but any hints as to what's causing this would be most welcome.

Otherwise, I guess I'll have to "hope" to encounter this when I can actually debug it...