Thread:Project:Support desk/Watchlist error after upgrade to 1.18.1

After upgrading from 1.10.1. to 1.18.1 the change of the watchlist using the link on the page does not work, instead the message MediaWiki:Watcherrortext turns up. Special:Watchlist works fine. I detected, that the target address generated by the link after action=watch&token= contains a different token as in Special:Preferences, if that matters. Any piece of advice is welcome.
 * MediaWiki 	1.18.1
 * PHP 	5.2.14 (apache2handler)
 * MySQL 	5.0.26