Most of the time it's driver issues. Since Dell broke it, call them and have them fix it.
As this is not my machine I won't know the exact drivers to use. You or your support staff will know this.
Bob
I've had my system -- consisting of a Dell XPS laptop running Win 7, 64-bit OS, with 6 gigs RAM, a Dell 21" flat screen external monitor, a Toshiba Dynadock U universal docking station -- working flawlessly for about a year. I had a Dell technician replace the XPS's motherboard a few weeks ago, and my techie replaced the hard drive with a solid state hard drive. After these upgrades I was very pleased because the system was working flawlessly...until I started a job in Photoshop CS5.
I started to see my laptop's wallpaper in Photoshop, where the photo I was editing should have been. The photo appears in the PS Navigator box, but not on the large screen area where it should appear. Also, grabbing either the right side, the corner or the bottom of the photo frame fails to enlarge the photo area. It instead duplicates the frame's edges, but does not increase the image size on the external monitor screen. If I open the clamshell and view PS on the laptop's screen, PS works just fine.
When viewing my MS Outlook 2010 emails and closing them, they take a split second to close, unlike before when they would close immediately. If I have to open another program while PS is open, these other program's screen shots pop up inside the PS screen. And then everything on the external monitor freezes. There is a sync issue between the external monitor's screen images.
Has anyone out there run into a similar problem, and if so, can you offer a possible solution?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic