'DWTS' Star Karina Smirnoff -- Another One Bites The Dust ... Fiance #3 Calls Off Engagement

"Dancing With The Stars" pro Karina Smirnoff changes fiances as often as she changes dance partners -- partly because dancers lead sexually charged lives ... this according to her latest ex.

Sources close to Jason Adelman -- who announced he and Karina were engaged in January -- say he called things off because she has "different family values." We're told he's not accusing her of cheating, but he was uncomfortable with the way she acted around other men ... especially dancers.

It's not like this was any long term engagement -- he just popped the question in January ... after they reconnected at a holiday party in December. As for his belief that dancers are all horned up people looking to bang -- a rep for Karina says that is "disrespectful and insulting to the entire dance community."

Our Adelman sources add that he feels Karina's track record speaks for itself ... she's been engaged twice before -- to fellow dancer Maksim Chmerkovskiy and MLB pitcher Brad Penny -- but never made it down the aisle. So much for the third time.

Karina's rep also says this is "nothing less than an attempted smear campaign from a malicious person."

For what it's worth ... we're told Karina returned the ring.