New install of Ubuntu 9.04 - resolution not set - nothing on screen

[carusoswi]

I installed 9.04 on my wifes Gateway desktop just now. She was already running 8.04 and XP. I installed 9.04 as a third OS. When I boot to 9.04, the login screen appears, then, a box floats from the lower right to upper left containing the message that the default resolution is not set, and offers what the optimum should be. Other than that box, I have a blank screen. Mouse pointer is present and responsive, nothing else.

I can re-boot and get back to 8.04 or XP.

Suggestions?

Thanks.

Caruso