After installing both Gmameui and the Sugar desktop session package I was not able to click on anything inside applications. I can close, minimize, and maximize windows and use the panel and desktop icons but the rest of the system is unusable. I have not deleted the partition in which this system is installed on, but have re-installed Ubuntu in a new partition, so if anyone can help me with this, it would still be of use to me.
I had the same problem with Sugar, found the answer at ubuntuforums.org
You don't need to delete the whole .gconf folder, edit the file
delete the tag with name "mouse_button_modifier", in my case this 3 lines:
mtime="1279125807" type="string"> disabled
and that's it.
Worked like a charm. Thanks, moiesk.