Problem with changing graphics card "driver"

Hi, thanks for reading.

I had installed Ubuntu 11.04 with the "Experimental" driver for NVIDIA cards, which right now I'm using.

I tried to change the driver to the NVIDIA's proprietary one, for higher resolution.

The problem that comes up after restarting (to load the new driver) is that my window sizes CAN NOT go beyond the size they were last time, or the window becomes an empty one, just the window, with it's border.

So, to be able to use my system efficiently, I've switched back to the experimental driver (everything is good with it except the resolution).

And oh, as you should have guessed my monitor is CRT (which I believe is better than LCD in theory, and most of LCDs, in action).

I guess the problem is with some config file, which's resolution value doesn't change with driver change, but I don't know which file, if ever my guess is correct.

Can you tell me what's wrong? and how can I fix it? Or I'd better keep using the experimental driver?

Thank you!