Is trouble on the horizon for Mark and Lexie on Grey's Anatomy? You knew there had to be. Here's what executive producer Krista Vernoff tells TV Guide about that couple ...

Q: Do you have any Mark/Lexie scoop for Season 6 of Grey's Anatomy? Love them!

A: I know you won't believe it, but they're going to have problems. "They've got some obstacles for sure, but some of our more emotional moments have come from them," Grey's Anatomy executive producer Krista Vernoff reports.

That doesn't mean the coupling won't survive, however.

"We've done a lot of stories about people coming together, and now we have an opportunity to tell stories about people who are together," Vernoff says.

Now that's something we doubt people can argue with.

Steve Marsi is the Managing Editor of TV Fanatic. Follow him on Google+ or email him here.