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THIS is why Mario and Karina broke up, as X17online was the first to report, back in April -- and despite recent efforts to patch things up, their relationship was basically OVER months ago.

Mario had been seeing Meaghan Cooper, a former Hooters girl during his trips to San Antonio, TX and when Mario's Dancing With the Stars girlfriend Karina found out, she was pissed!

Remember this video (CLICK HERE) when we asked Mario how things were going with Karina? Were YOU convinced?