This is certainly something that wasn't on Robert Pattinson's birthday wish list.

Sources say he and Kristen reportedly got into a heated argument on his 27th birthday on May 13, according to Hollywood Life.

Instead of spending the day going swimming with Rob and doing other carefree activities as she had planned, Kristen instead went to a friend's house for a tense, nearly hour-long phone conversation.

“Kristen was pacing back-and-forth in her friend’s apartment, smoking," according to an onlooker. "She looked really upset, talking on the phone for almost an hour — I’m guessing she was talking to Rob."

"She was really animated, like she was trying to explain something," the eyewitness continues. "She was getting frustrated and seemed very emotional."

After the phone conversation finally ended, K-Stew and her friend then drove to a different friend's house, where Kristen and the friend then sat in the car and talked for 45 minutes. Sounds like a blast.

So is this really as bad as it looks? It appears that the only sources here are "onlookers," so we're not fully convinced that there's indeed trouble in paradise for the Twilight couple.

Still, it is strange that Kristen would spend so much time talking with her friends on Rob's birthday, rather then, y'know, actually hanging out with Rob.

Given that Rob and Kristen had been so happy lately, we're hoping that if anything, this is just a momentary tiff. We can't deal with a permament Robsten split, you guys!

Source: Hollywood Life