I have wordpress 3.4.2 installed since december, but today I got this problems:
- the visual/html editor tabs disappeared
- the media upload does not work
I tried clearing cache, disabling all plugins, setting Twenty Eleven theme, replacing wp-admin and wp-includes folder with fresh versions with no result.
I found similar problems on the net but none of the solution fixed my problem... there is a common problem the makes the html toolbar disappear, but I think my problem is another one :(
Here are the screenshots of the problem: