sorry for the late reply,
firstly what I want you to do is update all your drivers and software relating to your graphics card. (this should fix some of the problem)
Secondly when you go to into display settings to "resize your desktop" does it just say monitor, or does it say Dynex-(model no) on Nvidia GTS 250.
Unfortunately alot of these TV's (especially the generic ones) have alot of bugs to them, whereas sony and samsung and LG check their tvs thoroughly and then update the firmware on the tv's the cheaper generic one's are often left in the cold.
But updating display drivers can do wonders, so check it out at the manufacturers site Drivers - Download NVIDIA Drivers