When I try to export a document from org-mode in emacs, c-X, c-E now results in 'Can't find library org' whereas in 10.04 it opened the export dialog allowing me to produce html, pdf etc. from the source org file.
Searching with Google, I found this bug for redhat which looks closely related.
The trouble is I don't know how to get hold of the emacs-el package it talks about in ubuntu in order to try its workaround so I'm currently stuck.
Depending on which version of emacs you are using, you can either install the emacs23-el or emacs24-el package.
That seems to work around the issue here. There is a similar bug on launchpad: https://bugs.launchpad.net/ubuntu/+source/emacs24/+bug/1172214 , so it seems like it may be a bug in emacs24.