my extra screen registers but doesn't show up
 

Hi guys, here's a bit of a weird one.

I'm running mountain lion 10.8.3 with display link driver 2.0.

when i plug in my adapter the computer automatically recognises it. If I go into displays in system preferences it lets me choose all my settings, and even recognises what brand and model screen I have connected.

However nothing is displayed on the screen. I've tried adjusting the resolution, switching between mirror modes and extending displays. Nothing.

I've tried a couple of different vga screens, and a hdmi tv (I don't have a dvi screen to try) Same thing each time - my computer registers that there is a screen there. It tells me the brand and model, even works out the best possible resolution for that screen. Then it proceeds to do.....nothing.... It's like the drinks machine from the hitchhikers guide to the galaxy....

Anyway I appreciate any possible solutions!