Screen Resolution messed up

[Charles Malespin]

Hi all, I just rebooted just now, and my screen resolution is all messed
up and too big.  I tried to change it via the system and pref manager
and got this error
The X Server does not support the XRandR extension.  Runtime resolution
changes to the display size are not available.

I dont know what this means or why it did this.  The only thing that I
have changed recently was I went from the standard video drivers on an
ATI Radeon X300 to the binary ones from the Ubuntu web site(btw how can
I change back to the original ones?  I am getting choppy video when I
run things full screen, even though I thought that since my processor
was fast enough to deal with it, 3 Ghz)  Any help or ideas please....