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 http://www.marketingcompass.co.uk/blog 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?