Wiki plugin seems to create a problem for me after I'm updating my wordpress to 3.1 and buddypress to 1.2.8. You can test it out at blogmyway.com sidebar.
The error is that it won't allow regular users to create a new page inside wiki even though I clearly allow network users and other users to add wiki pages.
Using Wiki version 1.0.0
Update: I should clarify, users could not create new content or page inside wiki of site admin's wiki. Nonetheless, users could edit a wiki post that site admin allows users to edit. When wiki isn't working, the error is You are not allowed to edit this post.
Oh one more thing, as site admin, I did create the wiki with privileges of Network Users, site users, and users who can edit posts in this site.