Washed Up on the Potomac, now playing at the Flea Theater’s new Tribeca home, is a dark workplace comedy set in the proofreading office of an ad agency (or possibly purgatory, depending on your interpretation). The show opens with a proofreading disaster in the office, a very obvious and costly mistake on an iPod ad, and the boss is looking for a scapegoat. There is the harried and mousy Sherri (Crystal Finn), who is dominated by her religious fundamentalist mother; Kate (Jennifer Morris), a wannabe rocker who won a songwriting contest at a young age but lost her momentum due to a family tragedy; Mark (Adam Green), a novelist who is so critical of his work that he rewrites the same passage again and again and never finishes anything; and Giorgio (Debargo Sanyal), the office’s self-serious manager who wishes everyone would act a little more professionally.