For some reason, the screen lock appears to be broken when I use separate x screens (it works fine if I use twin view or just one monitor, though). If I wait for the screen to lock (or if I tell it to lock), it fades to black, showing only the mouse cursor. However, when I move the mouse to bring up the password prompt, nothing happens, the screens remain completely blank.
Furthermore, it would appear that the screen lock never activated in the first place, for two reasons: one, if I blindly enter my password and press enter, nothing happens; and two, if I press ctrl+alt+delete and then enter it logs me out (which shouldn't happen if the password prompt is there, right), losing any progress I have on any of the open programs (meaning, not a very friendly option for a programmer ;) ).

So yeah, does anyone know why this is happening, and how to fix it? Thanks!

Notes: I am using Ubuntu 11.10 64 bit. I am using gnome-classic, but the same problem occurs when I use unity. I do not have xscreensaver, nor do I have any screen savers running (except, I guess for the default blank one).