Here's the way it went down ... Kovac Media Group served as Tyler's personal manager. They negotiated a great deal for the Aerosmith frontman to judge "American Idol." At some point, Kovac brought in a lawyer -- Dina LaPolt, to help negotiate a new deal for Tyler at the end of last season.

Kovac claims LaPolt was the ultimate Benedict Arnold, trashing Kovac to both Tyler and the honchos at "A.I." The lawsuit Kovac filed against LaPolt -- obtained by TMZ -- alleges she sucked up to "A.I." execs by disclosing Kovac's negotiating strategy, which ironically also hurt Tyler.

As for what that strategy was -- the suit claims Kovac was gunning to get Tyler an additional 6-8 million bucks in the current season.

According to the suit, LaPolt was so poisonous and underhanded, Tyler fired Kovac and kept her. The suit claims LaPolt screwed the negotiations up so badly, "A.I." offered Tyler no raise and he decided to walk, but he got a severance check from "A.I." and agreed to give Kovac its fair cut. The suit claims LaPolt screwed Kovac out of that commission as well.

The suit never mentions Tyler by name, but informed sources tell us he is indeed the artist who is at the center of the case. Tyler is not named as a defendant.