[TYPO3-english] File handling error

[Gunnar Jonsson]

I have installed typo3 6.2.7 and the introduction package with Bootstrap. Everything was in order, but suddenly it is not possible to "Add image" to a content element from fileadmin, because this generates an error message "Error 404 - not found". Even if the image really exist in fileadmin. If I try to "Edit content" in a CSS file in fileadmin, the file comes up fine, but when I try to save it I get the message "Page not found - because tce_file.php not found". Is there anyone who has an idea what is wrong? Or how to proceed to find a solution?
Regards,
Gunnar Jonsson