Yea, like MarathonManiac, I've suffered from multiple running injuries. It's hard when I cycle through building up, breaking down, and then having to rebuild when while not even getting any races in is extremely frustrating so I feel your pain. A part of me wants to throw in the towel, but the problem there is that I'm taking it too seriously and not keeping running in bounds with being a recreational activity, but rather I'm making it a stressor. That's what leads to injury and burnout I think. I mean our bodies and minds can only handle so much stress and we usually have plenty of it with our careers, school, families, or all of the above.
I think you actually sound kind of burned out. Maybe cut out your hard runs, and run to maintain some level of fitness, then re-evaluate when you feel motivated again? If you just finished a marathon you need a recovery month anyway.