Image uploader to Posts not working

Hello,
I have been having some problems with Image uploader (or any other uploader – media, sound,…) – mostly it doesn’t even open after the clicking on any of the icons. When it does it loads the uploader over entire screen (insted of popping out a dialog window) and after clicking anything to close it (Insert loaded image into post, etc…) it exits to blank screen.

It works fine on pages – the dialog window pops up, image gets loaded and the inserted into page.
The problem only appears when I’m uploading images to Posts.

I have tried to:
1. disable plugins and enable one by one
2. delete wp-admin and wp-include and replace by new ones
3. install alternative upload (Worpress Flash Uploader, Disable Flash Uploader)

None of these work.

Please I would be happy for any suggestions.
Thank ??