It sounds developmental to me, but I could be wrong. I have read that when babies hit milestones, like walking, crawling, etc. that it can certainly disrupt sleep. It is such a huge developmental leap; he is now seeing the world on his own, and from a totally different vantage point, so his brain has a lot more to process. Just my two cents. I don't have a solution for you, except to try to wait it out. Maybe check out the topics under "Getting Back on Track" on the sleep boards? They list milestones as a reason for sleep disturbances!
Good luck to you!
Amy