I recently upgraded to lion 10.7 and now I can't open itunes or do any software upgrades. Not even 10.7.1! Help

I just upgraded to lion 10.7 and when I tried to use itunes an error message came up saying that itunes may not work with this version of Mac OS X. So I tried to update my software, starting wtih 10.7.1 and it said "Mac OS X update cant be installed on this disk. The volume does not meet hte requirements for this update."

I have 48.19 GB on my HD so I'm not sure why it's saying that. I tried to do skip ahead to 10.7.5 and it said the same thing.