member's posts not attributed any more

I’ve recently allowed my members to add blog posts to my site, it’s been working ok, however now when you go to and check out the articles written by members – their names and links no longer show – this is the same when you’re in the ‘dashboard-posts’ section of the backend.

The user’s avatar is still there and if you click on ‘dashboard-users’ you can still that a member has written a number of posts…

Any ideas?