The term mortal sin had not been coined when Paul was writing.  According to Wills, this passage referred to eating at the Agape meal, although MSW does not seem to like the book where this analysis takes place.  I agree with LSN on one thing, the long-misunderstood doctrine on Communion and sin needs more formal reconsideration rather than pastoral adjustment.  Too many feel too guilty subjectively on what is not sinful at all for most.  Catholic divorce should also be codified.  Sometimes one spouse hurts another or two spouses hurt each other in ways that cannot be mended without having to claim that marriage was somehow invalid.