Monitor detected In System Preferences, but stays in standby

[JP8811]

Hey,

So i'm running Mac OS X ML 10.8.3 with the DL 2.0 drivers.

When I plug my monitor in, my mac screen goes blue and comes back (like it usually does when I plug a monitor in) but rather than the monitor turning on at this point like it does with thunderbolt, it stays in standby. If i go into system preferences, the monitor shows up and i can adjust resolution etc but it just never turns on..It's working fine via thunderboltVGA.

Any ideas what it could be, or anything I can try?

Thanks!