Thread:Extension talk:CheckUser/Error Installation OK but not possible to grant rights checkuser

I am using: nightly CheckUser-master-d293a77 MediaWiki 1.18.1 PHP 5.3.4-dev PostgreSQL 8.4.7

Output of "php install.php" was ok. After require the Plugin in LocalSettings.php I have on Special:UserRights the option to add the right "Check User". But if I submit the form I come back to Special:UserRights and get an ERROR 500. If I try to change other rights than "Check User" the same error happens. Only if I comment out the plugin in LocalSettings.php it is working again.

Where could be the error?

Thanks