All I can remember is the basic outline of what happens in the movie. Okay, here goes. It's about a woman who tries to get married but is already married to some guy. The actress (from what I can remember) is a cross between Cameron Diaz and Gwyneth Paltrow. The part that's sticking out for me is when she's in what I think is a registry office, and the guy behind the desk tells her that she's already married. Please somebody help, LOL. This has been annoying me for ages!

Is the movie Sweet Home Alabama with Reese Witherspoon?
That's all I can think of at the moment.
I hope this answers your question. :)