I cant suggest what could be the cause, but if you dont mind spending the time, there is a few things you could try to help eliminate the problem.
You could un-install and re-install everything, making sure that when you re-install its done in the correct order, which is :
1. Update any and all Drivers, graphics card, motherboard, network and DirectX redist. the whole lot.(shouldnt really matter if your drivers are at least recent, but its good to keep them updated anyway)
2. Visual Studio(make sure it's run at least once after it's installed and before anything else is installed, it needs to set some environment variables for itself)
3. DirectX SDK August 2007
4. DarkGDK
5. Any addons that you use.
That might not make a difference, if it doesnt, then at least you will know that the problem isnt related to your software installation and is more than likely related to either a software driver not playing nicely, or a hardware conflict....
What kind of PC are you using ? Is it a standard desktop type pc, or is it a notebook type ? (just asking as notebook hardware can sometimes cause strange conflicts in graphics apps) If its a desktop, how old is the hardware in it ? Could it be a conflict because of the age of hardware do you think ?
Sorry if none of that helps, im just throwing ideas at you, maybe something will help fix the problem for you, I know that the whole installation and uninstallation thing can be a pain in the backside and take ages, but like I said, at least it would eliminate your software as the cause.
Good Luck, this is definately a strange problem and I hope you can get it sorted
If it ain't broke.... DONT FIX IT !!!