Screen is Black for Video Files

Here's an interesting problem.

As of today, I can't see certain video files, when I open them in Windows Media Player AND VLC.

The sound is all there, it works fine, but the screen is blank. It just stopped working out of the blue, as everything was fine yesterday.

I'm using a Diamond Radeon HD2600 XT videocard, with the 7.3 drivers.

I reinstalled my sound and video drivers earlier today, and it worked for a bit, but now it's not working anymore.

How can this be, and what can I do about it?

 

Alright, almost an hour after posting this, things suddenly went back to normal.

The next day, it was back to black, and it is STILL like this.

I don't know what to do. The audio plays back fine, but no video appears at all. Just a black screen, no matter what filetype, and no matter what media player (tried VLC and WM).

Help?

EDIT: Okay, in Catalyst Control, there is an option that you can check "Reduce dvi frequency on high-resolution displays ". This solves solves my problem, as the video now plays. What i'm wondering: will this negatively affect my display performance just to get the video to work?