mountain lion server - web services wiki only work on host computer
I'm sorry to post this as an answer instead of a comment; I don't have enough Reputation here to comment.


Can you ping the server from another host?
If you can ping, try firing up a terminal with tail -f /Library/Logs/wikid/error.log and see what happens when someone tries to access the wiki service - that'll give you something to work with


Alternative to tail, use Console.app from your /Applications/Utilities folder