I have two external monitors in my MacBook Pro - the main one is connected via DisplayPort, and the secondary one over USB. I have the laptop set up to sleep the displays after 15 minutes. (And is the primary display -- it has the menubar and dock), This works most of the time, but sometimes the main display stays on all night, with the other two (the laptop screen and the USB one) off. This only happens sometimes though, and I find if I reboot or something it fixes itself.
It is sooo annoying though, and I'm worried about burn-in if the monitor stays on accidentally for a few days. Does anyone know what could be causing this? The energy saving options are, for plugged-in: Display Sleep: 15mins, Computer Sleep: Never