I've completed an upgrade from 206 to 2.1, and everything went just fine. I went to edit a post, and insert a new picture. Upload went fine, although I don't like the new way images are presented because it defaults to link to the image, but oh well.
So I insert the image, and then want to edit its properties to give it a title, and align it to the left, so I click the insert/edit image icon, and the box pops up. I set align to left, give it a title, and hit update, and nothing happens. Hit cancel, nothing happens. Hit the X in the corner, nothing happens. The whole browser window is stuck. I had to reload the page to clear it off.
This is using Firefox browser. With the IE browser, the insert/edit box goes away when I'm done with it.