I think we are all going through the same thought process trying to figure this out. First thing I wanted to say was that you boiled off too much volume, but then I noticed you said you hit your mark. Then only thing I could think would be that your readings were wrong, or maybe not adjusted for temperature. Though I think you have said above that you are confident with your gravity measurements. When I read ajf's post I thought that had to be it, but you say you swirled it pretty good which is really the same as what I do and everything goes pretty routine for me.
I think we all may just be stumped here. There doesn't seem to be a logical explaination as to why this would happen. Another mystery only known by the beer gods it would seem. At 1.064 I bet it won't take much of this beer to get a good buzz going, let us know the FG and how it turns out!
Also, I just moved to Ocala, got a few beers goin since I have been here but I was wondering if you had any info on the water profile down here? Also is there a HBS up there in Gainesville or do you just buy online like me?