Forum Permissions

When a user tries to post in my forum (which have public visibility). They get the "Access Denied" message, even with public and private read and write permissions.

I can't really explain it, and I need help. My url is "http://talktype1.com/forum"

Thanks

Check your membership settings... 

 That is the user's membership preferences, in the membership settings, they are enabled. 

I know this seems dumb to ask but do you have custom memberships and are all of them enabled?I always set up a test account for each type of membership, that way I can go through and test the permission settings each time I install or adjust a mod.