[xubuntu] blank screen bringing up in 12.04

I have just upgraded from 10.04 to 12.04. The only problem I have now is if I try to bring up the system in generic 12.04 mode , I will end up with a blank screen and a message that says"Please reset system to 1072x 768 ....." which I have done so under displays management. But if I check the settings on my monitor by itself , it says current setting is 648x 745 and recommended setting is 1072x768.
The only way I can get the system up is by going into recovery mode and bring it up that way. What am I to do?