Ugh-Oh

I've always thought of marathon training as a tightrope act... a balance between training volume and injury. Just doing enough to get you to that peak of fitness, while still holding back just enough to stay healthy and avoid injury. Until last week, I thought I was doing a pretty damn good job of balancing and everything was coming along very well.
When I checked in last Wednesday night, everything was feeling good. The race had gone well over the weekend, my workout had gone well that night, and I was pretty happy with my progress. The next morning, however, I got up to do my morning run and about a half-mile into it my world exploded. I started having sharp pains in my right knee. The pain is coming from the front of the knee and is a pain that seems to only be present when I run or walk down stairs. I made it through that short (3.75mi) run and didn't think too much of it at that point. Later in the day I headed out for my second run though and the pain was there within feet of starting. I made it through 1.25mi and called it a day.
I was headed to the mountains for a relaxing break with my parents on Thursday night, so I planned to do my easy Friday workout on the elyptical to give the knee a rest from the pounding. It was feeling pretty good by Friday night, so Saturday morning I decided to give the run a shot on a treadmill and just see how it held up. I chose the treadmill so that just in case it started to hurt too much I could jump off and get on the elyptical. I survived the workout, going 17.25 miles on a treadmill at 8,400ft elevation while watching the entire history of Pirates on the History channel. It was a brutal experience. Unfortunately, it also put my knee into a pretty big amount of pain.
By Saturday afternoon it would hurt, but only when I was trying to walk down stairs, or bending my leg slightly. Sunday I went easy on the elyptical again.
I have now run for 77 days (11 weeks) straight, without one day off and although this week was to be my last really big week of training, I've got to make a big change to get my knee back in the game. I'm taking today completely off and will see what it's feeling like tomorrow to determine whether I will just run a little or will again take the day completely off. How freakin' depressing! I'm trying to tell myself that it's not a big deal and that after a couple easy days it'll be back to normal and good to go for the homestretch of training. I think this is where the mental craziness of endurance sports begins to play a role. I know that looking at the big picture, a couple of days is not a big deal, but it's extremely tough not to feel extremely down while I'm in it. I've put in so much effort to get fit... I just don't want to lose it, and more importantly, I want it to payoff! Ahhh well, if anyone out there knows any great things that I can be doing for it in the interim, please let me know ASAP. I hope training is going better for all of you at this point! Happy training!