I'm on google chrome, and this only happens when I'm on youtube, but a strip of blackness will appear on the right side of my screen. Here is a picture.
It just started happening right now, wasn't like this last night.
If it is just on Chrome that is the problem. I am not familiar with Chrome but with IE, there is a way to remove all addons. Do the same with Chorme and you will probably solve the problem. Then put the addons one at a time and test.
Can you uninstall and then install Chrome again?
Chrome has started to become less reliable under Vista lately. A few previous updates made Chrome behave a little strangely and cause flash to crash quite a bit. The latest version seems OK, except that I find streaming video to be choppy. It didn't used to be like this.
I was usng Chrome for a short while this year. It started loading its menus in a language I hadn't set, and couldn't read. I managed to get it back to english, and it changed it to another language. At that point I completely uninstalled it, and re-downloaded it. Installed it, started acting strange again. Uninstalled, I've never used it again.