When this happens to me, it's always the drivers. Since it's a laptop your choices are limited but make sure you make a warranty claim if they don't support it by some driver on their web site.
I just got a second monitor, plug and play worked and was fine even though my main (laptop) was 1280 x 800 and the second screen is 1024 x 768. It went to sleep. I woke up my laptop, and both screens showed the waking up loading windows, then the second screen went black. Before, it still let me use the second screen even though I couldn't see anything, now I can't extend to the second screen through display settings. If I try now, the laptop seems to get set to the lowest display settings possible, and the second screen stays dark. Help?