When stuff like this happens to me, I usually go through the install steps again to make sure I did the right stuff.
There was an issue a few days ago here: http://www.linuxquestions.org/questi...-flash-812697/
Did you look through that? Perhaps you have something different configured in your system and would be advised to first try reinstalling.
I see you cross-posted at linuxforums. Searching that forum yielded this: http://www.linuxforums.org/forum/ubu...t-version.html
There was no reply from the original poster so I assume that worked for him.
Lastly, whenever I install I simply do this:
It's worked on all my 64-bit ubuntu 10.04 systems so far (5 of them).