DMX SUED FOR COMEBACK TOUR THAT NEVER HAPPENED!

DMX is on the hook for another $630,000 -- this according to a booking agency which claims X's legal problems torpedoed a lucrative international comeback tour ... and now, it's suing to get its money back.

The booking agency in question -- a company called Heavy Rotation -- filed the lawsuit in New York, claiming it struck an exclusive year-long deal with DMX in 2011 to book the rapper's concerts ... anywhere on the planet.

But according to the lawsuit, DMX was plagued with legal problems from the start -- a traffic violation in August, and two nasty child support disputes ... which led to a lien on the rapper's passport, preventing him from performing overseas.

According to the suit, HR bent over backwards to fix the legal issues -- coughing up nearly a hundred grand to cover bail, child support, and a slew of other legal bills ... hoping it would clear the way for the tour, a task that included lifting the lien on X's passport.

But HR claims its efforts were in vain -- because DMX continued to cause problems, hiring outside management that tried to book DMX on shows within the United States ... violating X's agreement with HR. On top of that, X couldn't resolve his passport issues ... and all concerts had to be canceled.

X's manager Jason tells a different story -- claiming DMX chose to sever all ties with HR after it put the rapper at risk with some unsavory business practices.

Still, HR claims it lost $749,285 on the deal gone bad -- and it wants the money back, stat.

I couldn't find the clip of Couples Retreat that came on last night! But how the f**k is DMX gonna get on VH1 all coked up?On my Momma! That ni**a was on that white girl! He kept on biting down & wiping his nose like something was on itBut that's my Dog Though

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