We have four administrators for our site, due to its large
size. One of the administrators downloaded the trial version of CS3
to test it out. Now, since she used the administration features
with that version, none of the rest of us can use the admin
features with our version (3.1). It says "Your version of
Contribute is too old to administer this website. Please use a
newer version of Contribute, or contact another administrator."
If you kept a backup of the "_mm" folder on your site you
might could overwrite the newer copy of the folder.
Short of this I don't think you have any other options other
than upgrading. When upgrading the Administrative functions
Contribute CS3 makes changes to the formatting of the XML files
where the site infromation is stored.