Ok, DH and I have been TTC since Dec 08.
I can see how that is so confusing! It's not uncommon to have the occasional wonky cycle. A single cycle with late O, or even anovulation, is not uncommon for women with even the most predictable cycles.
When did you last poas? The spotting could be hormones, it could be AF coming, it could be nothing at all...it's hard to tell. I know that isn't much help, but if no AF and no +HPT I'd be riding my dr for some b/w.