'Locking up'?

[Jaded Misanthrope]

This may be the wrong place for this thread, and if so I apologise, but it is the best place that I could think of.

After I have had Ubuntu running continuously for a few hours (I'm using a laptop, if that is significant), it just starts to 'lock up'. Currently running programs are fine, but I cannot start any more (it says it is launching in the toolbar, but nothing actually visibly starts) and if I try to restart using the button in the top-right, the window with the restart option does not even appear--the button just stays in the pressed down position.

Can anybody shed any light on this?

[sayakb]

I have the same problem. Found that problem reduces after disabling compiz, but persists. For me, it mostly freezes when I open Totem (Movie player)

[Jaded Misanthrope]

Compiz is not enabled, but I still encounter this problem fairly frequently (frequently enough to be so vaguely irritating as to make me want to do something about it).