Unregistered users not allowed to see thumbnail next to category

[sicily18]

I'm having a problem with unregistered users at my site not being able to see the thumbnail of a picture next to the category name on the main page. The admin can see it, but unregistered users can't. Does anybody have any idea what to do, if it's in configurations or if its a script thing. Thanks in advance.

[Tranz]

Link, please.