Boots fine but screen is blank

downloaded the latest dvd version. burned the iso. booted. near as i can tell from all the messages it seemed to proceed normally. at the end, i have black screen; honking big mouse pointer that moves when i move the mouse; and some confetti stuff in bottom right of screen. so not dead. but no icons, no symbology, no response to any keyboard, function keys, mouse key presses. What is supposed to happen next?

i have a dual core i3 intel cpu; i also have nvidia boards on my system -- one for gpu development and the other is the graphics board. I also have two monitors, both attached to the one nvidia board: gtx 430.

booted to run mode 3.
keyboard works, mouse works, video works, internet works ( I pinged my router and yahoo).
so problem is that none of the X11 interfaces start correctly -- i tried the default, tried KDE, tried GNOME. all give blank screen but mouse works