People get hung up on 3 Act Structure in screenplays, and all it really leads to are "problems in the second act." These problems come because the hour long "second act" has no "turning points" or "act breaks" within it as described in most screenwriting books.
The truth is that 3 Act Structure is a myth; or more accurately, it is just one way, among many, to think about "structure." You can look at movies as having four acts, or eight (usually called sequences.) In this link, a very funny blogger makes a case for the 5 Act Structure of Iron Man. A five Act structure leads to more complexity and character development. (See Film Crit Hulk)
If it was good enough for Shakespeare and Romeo and Juliet, its good enough for your rom-com. :)