Was it Jason Alexander and John Cusack?
I am looking for a title name of a movie about a man (I thought John Cusack) who's girlfriend leaves the country with another man - leaving behind her weekly column job. When her publisher/editor starts calling their apartment looking for her work, he starts writing the column PRETENDING to be his estranged girlfriend - claiming she is always too sick to drop off her articles. After working closely with the publisher/editor they fall in love. Soon the girlfriend returns and finds out she has become a household name overnight (and it's all due to his writing) She blows his cover and discovers he has fallen for her boss. I believe that Jason Alexander (George from Seinfeld) plays his best friend and he has a stereotypical "New York" girlfriend. Please help, this is driving me nuts!