visual/html editor and media not working

Hello,
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:

http://s17.postimage.org/4n96ool8v/image.jpg
http://s17.postimage.org/ovwkaekjz/image.jpg
Any help would be immensely appreciated!