"Add files" and "Visual/text" switch not working since 3.5.2

Hi.
Since I’ve updated a bunch of wordpress installations to 3.5.2 today in the one using this theme the buttons “Add files” (hope this is the correct text in English, we’re using German setups) and the switch from text vie to the visual editor just don’t do anything anymore.

The code of those elements hasn’t changed, that was the first where I’ve checked and the pointer still indicates them as links but there’s just no action. No errors in the Firebug console either. It jstt looks like there’s no event firing for onclick.

Any suggestions would be appreciated?

Best regards
Floutsch