"undefined" when logging out?

[Linkz0r]

Hi I've just installed a new vbulletin board here and our having issues with logging out when logged in.

If you click logout from the nav link or the one at the bottom a pop-up message comes up saying "undefined" and says OK or cancel, a screen shot of it can be found here. I don't think I've touched any of the templates involving the log out part of the site so I don't know what's wrong, and when I click OK it comes up with

and then I click logout and it logs me out fine, but this is a hassle and I don't want to have to do this every time.

My login seems fine and there is nothing wrong there. Also over the last few days I have installed quite a few mods not knowing if that could have made this happen or not, though I doubt it did. Any ideas on what the problem is?