Lindsay Lohan has repeatedly declared how darn "happy" she is with Samantha Ronson, but even the most lovey-dovey couples can sometimes work each other's last nerve.

Case in point: A spy tattles to the New York Post that the perpetually hip-joined pair "had a quiet fight" on Thursday as they took the train from New York to Washington, D.C., where Ronson was deejaying a fundraiser for the Children's Miracle Network.

Sam and Lindsay hit the beach together in Los Cabos, Mexico, on Sept. 30. (©Clasos.com/Splash News)

Among the charges the starlet supposedly leveled at her inamorata during the trip: "I do what's good for you, not what's best for both of us" and "Don't [bleeping] lie to me!"

The paper says LiLo was also "whining incessantly and Samantha was trying to deflect it. When Lindsay would get up, Samantha would sigh and put her sweatshirt hood back up."

But all appeared to be forgiven by the club-set charity event that night, at least according to a stream-of-consciousness musings Lohan posted on her MySpace page while hanging out in the DJ booth at the hot spot.

"This blog isn't really intended to mean much," she wrote. "It's just something to let people into my life -- kind of a blog to let people know that I am working hard and I go out when Samantha is working because she's pretty great to hear and I love to be around her and her energy as much as possible."

Especially when her energy comes with expensive gifts. The London Daily Mirror claims Sam recently presented Lindsay with a $25,000 diamond-studded Tiret watch.

Chris Martin hits the Q Awards in London on Oct. 6. (©Retna Ltd.)

In other squabble news, is Chris Martin a crankypants or a cutup?

A buddy of the Gwyneth Paltrow-devoted Coldplay front man tells the New York Daily News that he was "just fooling around" when he thwacked a journalist at the Q Awards in London a few weeks back.

Seems Martin was chatting with a Q magazine editor when he jokingly mentioned how he and his missus, who are parents to Apple, 4, and Moses, 2, have a deal that gives them a free romantic pass with a pair of cheesy British pop acts: Girls Aloud for him and Westlife for her.

That's when the pop culture-blanking reporter allegedly zinged, "You could have at least told her Brad Pitt," leading Martin to rail, "She was engaged to him, you [bleeper]!"

An apology and a "fatherly arm" around his shoulder did little to quell the rocker's ire, according to HolyMoly.co.uk, which says he called the journalist an unflattering name and gave him a "swift blow to the chest." Ha ha?

Next: Jen Wooed by John's Warbling? Jolie on Rug Rats, Refugees