Thread:Project:Support desk/User's can't log into Wiki webpage/reply (3)

First things first: find out how the authentication is happening.

Also, what version of MediaWiki and PHP are you using? What sort of system is it running on? What is the version of the OS? The DB? What extensions are displayed on the Special:Version page?

You may consider hiring a consultant (like me) to help you upgrade the system and document it as well so that you can take over maintenance of it in the future.