I've had this same issue with TWO "clean" installs of 3.3 (not automatic updates) AND have seen it now in multiple manual upgrades to 3.3. Plugins & theme issues were definitely NOT the issue.
With each of the sites, we did a manual install of 3.3 onto the server. after the manual install, the sites wouldn't upload media into the posts (it would take you straight to the media uploader in the same page), the widgets lost all drag & drop functionality, the theme "preview" in the appearance-->themes area of the admin would open the theme preview in the same window (NOT as a lightbox). This indicated that there was a problem with JS in the admin area.
These sites were on different servers/hosts with different hosting packages/configurations, so it was not server or webhost specific problems.
I've done *numerous* automatic updates to 3.3 on other sites - again, different hosts, different hosting configurations - without any problems.
So, this is what I did to solve the admin JS issues & it's worked like a charm on every site that this has been an issue...
[keep in mind, if there were plugins, all of them were deactivated. ALSO, theme was set to default theme if applicable so that we were sure it was not related to plugins OR themes.]
1. Deleted ALL files from 3.3. (left database intact)
2. Uploaded version 3.2.x files on the site(s) that had the JS admin problems after manual installation of 3.3.
3. Log in to admin area. It gives a prompt that there is a newer version & asks us to upgrade. THEN we let it upgrade automatically to 3.3.
4. Cleared cache, refreshed pages. Everything worked fine.
Our experiences with 3.3 seem to indicate that there may be an error/bug in the full version available for download (for manual installs/upgrades). I can not repeat the JS errors on ANY site that I've done an automatic upgrade with - only problems we have seen are on sites that are upgraded/installed manually with the full version of 3.3.