Don't let the grammar Nazis get you down! If they've corrected you for misusing that for whom, starting a sentence with and, but and however, or gasp - the sin of "verbing" - fight back!
Jan Freeman of Throw Grammar from the Train blog has a nifty post over at Boston about English language rules that even the grammar Nazis got wrong. For example:
The girl that I marry. No, it doesn’t have to be whom I marry. “People that has always been good English,” notes Bryan Garner in Garner’s Modern American Usage, “and it’s a silly fetish to insist that who is the only relative pronoun that can refer to humans.” Choose who if you like, but to claim that using that “makes a person seem less human,” as Mignon Fogarty suggested in a Grammar Girl podcast — that’s just looking for trouble.
Since you asked. It’s totally legit to use since for because, unless it would cause ambiguity. Since has had its causal sense, as well as its temporal sense, from the beginning.