Samsung SyncMaster 750p... problems!

So... 'bout a couple of years ago, I used the software TVTool with the "fake" TwinView option (used both TV and Monitor displays at the same time on a VideoCard that didn't have this option).
Ok, they warned about not using this resource if the monitor couldn't handle the refresh rate.
I think my monitor had no problems with that (being a professional series and all) and I used...
Immediately, some weird image synch problem happened, but I solved it putting 100hz refresh rate.
Two years later (now) the problem is back, and changing refresh rates doesn't solve it! At least not permanently.
So here it is:
The image is ok. Then, 5 to 10 minutes... may be even 30 minutes of crystal clear image later, the monitor just goes crazy and messes the image up.
It's like the whole monitor is slip in pixel-thin lines that comes out of synch... like on line comes an inch to the right, the next comes an inch to the left, and so on.
Anyone had this problem and knows how to solve it?
100% shure it's monitor problem, given that I already tested it on 3 different computers...
Also, it's not gaussing problems, since the monitor itself has an degaussing option and it solves nothing...
Please help! There are no reliable technical support where I live...