"TribalFusion is one of the largest web advertisers on the net; there would be so many websites that these people would not be able to reach; I wonder why our's is the one that doesn't work."

Mayby it's how you handle the calls to Tribals server.

Just make sure Tribal is called after ShareCG's content is displayed. Or display tribals ads in one or more seperate frames/iframes. This is also known as poor mans web-multitasking, works in any modern browser and is also defined in XHTML (see W3.org).