I have just plugged in an old nVidia Geforce 6600 PCIe Gfx card and have set the revolution to 1600 x 1200 and have been typing away for the last 2 minutes without so much as a flicker!!
If I right click on the desktop and select screen resolution the monitor is shown as a Generic PnP and is not listed as a Samsung Syncmaster, I did managed to install a Syncmaster Driver and managed to get the monitor listed in Device manager as a Syncmaster but it still showed up as Generic in screen resolution and AMD Graphics Control Engine. I have also noticed now it has reverted back to generic in Device manager. I read a post about LCD monitors losing their EIDE (Or something) which is the built in EPROM used to tell video cards what the monitor is and what resolutions are supported. But this does not change the fact that my old nVidia 6600 works fine and the damm brand new AMD 5400K CPU with discreet Radeon 7540HD doesnt work!!!
So this is either:
1. A problem with the new AMD A6 5400K, which foolishly I RMA recently because the damm fan was cracked. (I am 100% confident that the problem did not occur with the replaced one as I was playing SKYRIM on high settings without a problem.
2. A driver problem with Windows 7 64 Bit / AMD Radeon 7540 built into the CPU.
I am airing on the CPU myself.