Mark Ballas and his girlfriend got in a 6 minute, alcohol-fueled fight over Mark's unforgivable sin -- smoking a cigarette after promising to quit.

The altercation flared up outside Playhouse nightclub in Hollywood just after midnight Tuesday.  We're told Tiffany Dunn was outraged that Mark had broken a deal they had -- she agreed to sell her scooter after injuring herself in an accident, and in return he agreed to quit smoking.  But one of Tiffany's friends caught Mark inhaling, blabbed to her and fireworks erupted.

Tiffany screams mid-argument, "You're such a d**k when you drink." For his part, Mark tells Tiff, "You can cry me a river for all I care, and you can swim in it."

Mark tells Tiffany, "You punched me in face 3 times today." She responds, "I was dancing."

Tiffany thinks Mark's fibbing about smoking is a gateway lie: "It makes me wonder what else you lie about. Yeah, exactly, exactly, exactly, what else have you lied to me about?"

At one point ... Mark yanks Tiffany's key chain from her, removes his house key and then hands the chain back. She pushes him and he leaves.

We're told Mark and Tiffany were "hammered," but all ended well. They got a cab together and went home.

Young love.

Mark Ballas tells TMZ ... he was NOT the target of a Jaleel White meltdown during a "Dancing with the Stars" rehearsal session last week ... despite reports to the contrary.

Mark was leaving Hyde in L.A. last night (the same one Paris, Lindsay and Britney used to party at back in the day) ... when we asked about Jaleel's alleged meltdown ... in which he reportedly screamed at his partner Kym Johnson before going off on Mark.

But Ballas says the whole thing is a "complete fabrication" ... telling us, "We're in L.A. man ... everything's fabricated."

"Dancing with the Stars" pro Mark Ballas has a MAJOR problem with the "Dance Moms" reality show -- telling TMZ, the angry screaming dance coach is verbally abusing the kids ... and she doesn't know jack squat about dancing.

In case you haven't seen the show ... dance company owner Abby Lee Miller has become famous for berating the children ... once telling a crying little girl, "You save those tears for your pillow, in your room, alone."



Mark tells us, "She's not dancing, she's just yelling at them" ... adding, "I just don't think it's the correct way to teach somebody ... Those kids are 6 years old. They're learning. They're babies ... They need to be treated the correct way."

Ballas adds, "Those kids should not be afraid to go to dance."

DISCLAIMER: We are not saying women are worse drivers than men -- BUT ... Mark Ballas' girlfriend totally just destroyed the "Dancing" pro's Audi SUV ... and TMZ has obtained pics of the wreckage.

The 3-car pileup went down Saturday night on the Sunset Strip in L.A. -- sources tell TMZ, Mark's Pia Toscano replacement Tiffany Dunn was driving his Audi and accidentally rammed some dude's Porsche from behind ... sending him careening into another car.

Thankfully, everyone was fine ... and the damage on the other two cars wasn't too bad -- but that's a heckuva lot more than we can say for Mark's poor Audi, which was left in undriveable condition in the middle of the road.

We're told the car was eventually towed to safety -- and Mark's insurance company is taking care of everything else.

So -- now that we got that out of the way -- we gotta ask ...

One night after celebrating her 31st birthday in New York City, Kim Kardashian -- along with hubby Kris Humphries, sister Khloe, brother-in-law Lamar Odom, and BFF Mark Ballas -- brought the party to Marquee nightclub in Las Vegas.

It's hard to keep up with a Kardashian on her birthday.

Mark Ballas may be a dancing machine by night -- but he's also a sweaty, half-naked ass-kicking machine by day ... and TMZ has the video to prove it.

We caught the "Dancing with the Stars" pro kicking, punching, and kneeing the crap out of his trainer at True Warrior Fitness in L.A. yesterday -- and we gotta say ... it's pretty impressive.

After the session, Mark said his trainer told him, "If you can dance, you can fight."

Apparently, Shia LaBeouf is not a very good dancer.

Not a good month for Mark Ballas -- two weeks after the "Dancing with the Stars" pro lost his hot girlfriend Pia Toscano ... some heartless burglar busted his car window and jacked his guitar.

Ballas posted the bad-luck news this weekend on his Twitter -- writing, "My car just got broke into and my first Martin guitar was taken..."

To make matters worse, Ballas says his super-expensive Breitling watch was stolen earlier last week.

On his way out of "DWTS" practice, Ballas told photogs he'll pay good money to get Marty back.

The relationship they said would never last ... didn't last.

"Dancing with the Stars" pro Mark Ballas and "American Idol" hottie Pia Toscano have officially broken up ... according to People.com.  The split is said to be "mutual."

Mark is currently training with his "Dancing" partner Kristin Cavallari ... and Pia ... is ... um ... well, she's still hot.

"Dancing with the Stars" stud Mark Ballas single-handedly raised more than $12 THOUSAND for the elderly last weekend -- all because he forgot to bring a change of clothes to a charity benefit.

Mark volunteered to perform at the 4th Annual Avamar Foundation benefit in Warren, Ohio -- representing The Beat of Ohio dance studio -- but we're told, he only brought one outfit ... and after performing ... had to borrow a shirt from the host.

Sources at the event tell TMZ Mark was so moved by the benefit, he decided to sign the shirt ... and auction it off. He also threw in front row VIP tickets to 'DWTS' for two nights, backstage passes, and pictures with the other dancing pros.

All the swag raked in $12,500 during the two day benefit.

Private dance lessons from Mark Ballas usually run $300/hour ... but TMZ has learned Kim Kardashian won't have to pay the guy a cent ... because he REFUSES to take her money!



Mark has been hitting the ballroom floor with Kim and her fiance Kris Humphries in preparation for their GARGANTUAN wedding ... where the couple plans on performing a waltz for their first dance.

We're told K&K have been practicing up a storm over the last few weeks -- but Kris "is a perfectionist" when it comes to his footwork and has INSISTED on more training.

Kim and Kris have tried to throw some cash at Ballas for all of his help, but the "Dancing with the Stars" pro -- who was just nominated for an Emmy -- simply won't take payment from his former celebrity partner.

So ... does he still have to get them a wedding gift?

 

Defendant: "Dancing" pro Mark Ballas -- accused of firing his ex-publicist and NOT paying.
Plaintiff: Ace PR -- accused of doing a CRAPPY job. 

Strap on your rhinestone pants ... 'cause this one's about to get NASTY!!!


Ballas has just been hit with a summons to appear in L.A. County Small Claims Court -- because Ace PR claims the "Dancing with the Stars" pro never forked over $2,637.75 he owed the company after he fired them back in September.

According to legal docs, obtained by TMZ, Ace claims Ballas agreed to pay them a "30 day termination fee" when he signed his contract ... which is basically severance pay.

But sources close to Ballas tell us ... the dancer believes he doesn't owe Ace a dime, because they breached the contract by doing such a terrible job.

Ballas and Ace PR are set to face off in small claims court on July 8.

Stay tuned ...

UPDATE: A rep for Ace tells TMZ, "After patiently waiting for this issue to be resolved, for close to a year, we hope that this can get settled and we can move on."