Hi, I just thought this might help someone else if you had the problem (and big headaches!) that I had. I had the Twenty Eleven theme and updated it on June 13th as needed. But all of a sudden my menu buttons wouldn't work nor some in the sidebar. It took a couple days and some help from MaAnna from BlogAid, but it ended up being the WordPress SEO by Yoast plugin! I deactivated that and everything came back!
Now we know that plugin is excellent, and I'm sure he's working on a fix. I'm hanging on to it to reactivate as soon as he tweaks it. Hope this helps to solve someone elses troubles!