It's in my field of study, in my specialization, and in a course offered by one of my profs that'll be giving me a LoR. That last point speaks toward resolving it later/letting her explain it in her letter, but it's an F and it tanks my GPA, my major GPA, and the whole idea of doing this grad school thing. Plus it's fucking annoying because it's from spring 2008. Details in tiny text: I'd taken an incomplete and submitted the paperwork and all relevant materials to the relevant professor well in advance of the deadline. This professor is very flaky but absolutely brilliant and a fabulous teacher/mentor. I have no doubt my grade will be an A in this class, I just need her to submit the paperwork to the university. It's a matter of hand-holding, honestly. But I work 9-5 M-F, campus is a bitch to get to, she's now on leave, her office hours are always VERY crowded and take 4+ hours which I'd have to take off work, blah blah blah excuses.
I'm not waiting until deadlines time to talk to people. I'm putting together a rough draft of the relevant application pieces (statement of purpose, writing sample, summary of academic achievement/CV) this summer, and I'll be approaching them directly in ~August, with a warning/feeling out contact sometime between April and June. ESPECIALLY with this flaky-but-awesome prof, I know full well it takes months and months of advanced knowledge to get these things right. Lucky for me, a superstar in my field respects my work, and a rising star totally loves me. So woo for that.