What caused the falling out between Jennie Garth and Tiffani Amber Theissen?

Does anybody have any first hand knowledge on what caused the fallout in their friendship?...

Though their relationship started out rocky, they became really good friends, and Tiffani was even a bridesmaid in Jennie's wedding...

At some point, they had a falling out, and both women have been tight-lipped. Tiffani would say on Howard Stern that it had nothing to do with the show, and that she "was the one that was hurt"...

I speculate that Jennie accused Tiffani of coming onto her husband at the time, Peter Facinelli. They did do a show together at one point(Fastlane), and I could see Jennie being the jealous type, but who knows?...

I don't believe their falling out had anything to do with Tori's first husband Charlie, as some speculate...

I know this is none of anybody business, just curious...