We updated to 3.3.1 from 3.2.1 last week, and everything seems to be working fine. I was updating a CPT we created, adding a new sponsor item, and I noticed that after adding a featured item, clicking save in the media uploader, and then clicking the "X" to return to the editor screen, the grey modal background remained...rendering the rest of the page useless. I linked to screen cast of this. To debug, I checked to see if the problem existed on posts/pages. With These Post Types there was no issue, which makes me think my code for the CPT is causing the problem. I've pasted it below...maybe someone can spot something.
One thing to note, is that I have my CPT's in a core functionality plugin to keep it independent from the theme. I don't think this matters, but figured I would let you know.
Screen cast: http://vimeo.com/35155467