Guests cannot post links?

I have a problem on a Forum Called http://rpg-haven.forumotion.com/forum . It has a section where guest can advertise their forum on ours and for some-odd reason. Guest cannot post a direct URL link to their forum. It just shows up blank. If they however did something similar to the code below they would be able to link. But I fear that their ignorance will be harmful to their advertising.

Code:

<div align="center"><a href="http://rpg-haven.forumotion.com/"><img src="http://i98.photobucket.com/albums/l245/elwrick/coolte11-1.png" border="0" alt="Photobucket"></a></div>

I found that if a member posts a regular link on the same forum it shows up normally. This I assume means a permissions problem. I have looked at all of the permissions and I dont see anything that could be out of place. What would the permission be for guest linking their ads?

Here is a screenshot of us testing this problem... One where its us testing as guests to put the homepage link in, and one with a member placing a link as a test.

Spoiler:

How would I go about solving this?