Sources say that it was Aniston’s over-clinginess and jealous behavior that resulted from Pitt’s betrayal, which drove Vaughn to call it quits. However, it has been reported that Vince never actually cheated on Jen; it is merely easier for her to blame him for problems in the relationship than to confront her own issues stemming from her failed marriage. Since the break-up, Jen has been laying low, staying home and spending time in mediations, while Vince is living up the single life, partying with Kevin Spacey and filming a new movie, and avoiding all contact with depressed and vulnerable Jen.

Looks like Jen had reason to worry. Vince Vaughn was seen publicly cavorting with a mystery blonde in London.

The 'Dodgeball' actor arrived at the aftershow party of '24 Hour Plays', a
London theatre production he had appeared in, with a stained sweatshirt and
his fly undone and then began canoodling with the girl.