Graphics or Screen Problem

[Mango777]

Hello, i just got a new LG screen (E1940) for my pc. Im running a MSI ATI radeon HD 5750. When i got the screen installed everything ran well until after watching some videos on youtube made the screen blur, jump and flicker. This wouldnt go away when i restarted. I went to the device manager and deactivated the graphics card and all the flickering and stuff stopped which has led me to believe its a graphics problem. Any thoughts on this?

 

[Mango777]

Running i5 650
Gigabyte H55M USB3 motherboard
4gb Ram
Windows 7 Ultimate
Ati Radeon HD5750

Also when i connected a new screen it seemed to be fine so im a little confused as to how to comfront this problem. Any help will be greatly appreciated.