I watched this recently as it was on iPlayer and okay, I know it was just a stupid mindless film but ARGH!
Basic storyline is, Uma Therman's character runs a radio chat show giving out relationship advice. A woman calls in who is unsure about her upcoming engagement (she's known the guy five months 
) Uma's character (who is a bit of a Leave-The-Bastard, hold out for higher standards kind of advice giver) doesn't expressly tell her to dump but from the phone call she decides to.
Just as a coincidence, the fiancé of the caller happened to be listening too and goes on a rampage about how Uma's character "ruined his marriage" and decides to get his own back. (Mature bloke, here) So he gets his teenage son to hack into the government records (As an aside - really?? Okay sorry, back to the feminist raging.) and set her as being married to him. So when she goes to register her intent to marry her real fiancé, she can't until she gets this marriage annulled.
Anyway so the rest of the film is her tracking him down and then a load of crazy manipulative stunts he pulls because (surprise!) he decides he rather likes her, even when she makes it clear she's not interested. I couldn't actually be bothered to watch the last 20 minutes, but the message of the film seemed to be, don't bother holding out for a decent bloke because they're all boring, instead go for a gaslighty, immature manchild because he's SPONTANEOUS!!! and basically disregard all actually useful relationship advice, ever.
Remind me why I don't watch films any more?