Having looked through your other log, it seems to me that the reason you forgot how to squat is that you haven't been doing it for a long time. Your box squats are very impressive - I'm not sure if I could take 150 to my box raw 5 times but if you are struggling to free squat your box squat 5RM then there is obviously something wrong. I can probably do it with ease looking sideways, up, down, at my dick -- wherever, and I think I might speak for most people when I say this. In my opinion a 150 x 5,5 box squat should be transferring to close to a 182.5 free squat now, not in June. It could be that there is just a lack of practice that makes your form bad when you don't have the box there, or it could be a weakness caused by only box squatting. Box squats, done as Louie says (I can only guess that you are doing them like this, since I know you like Louie), will be very heavy on the posterior chain and light on the quads, due to a fairly open knee angle and a lot of sitting back. The quads are necessary for raw free squatting since you still have to extend your knees.
I am of the opinion that weak quads will result in leaning over, as explained here (yes, I know it's Mark "The Moron" Rippetoe's forum, but relax - it's someone else's post)
http://strengthmill.net/forum/showpost.php?p=27630&postcount=9. My videos of squatting in wraps also seem to support this.
http://www.youtube.com/watch?v=WRxfFiCWxqI My quads are artificially stronger than usual because I'm wearing wraps, and if you look at the second rep when it gets really hard, instead of leaning over I actually lift my chest, which pushes the knees a bit forward and finishing the rep like that - in other words by doing the complete opposite of a good morning. Quad weakness would be consistent with your journal. You don't really seem to train them that much apart from with light weight on a leg press.
If your 1RM testing was done to a box then this post is probably a waste of time. But still something to think about for when you do start to free squat, which is necessary if you are going to be a powerlifter.