[TYPO3] Thumnails images not showing in BE

[Antonio Willybiro [awillys]]

Hi,

My thumbnails images are not showing up anymore in the BE.
I have the "X" mark instead. I don't remember what i did that may have 
caused it.
I tried to unistall all the extension but it did not help.
I checked anotherT3 installation that i have on the same server and everythg 
work fine there.
The corresponding images are displayed correctly in FE.

Any clue?

Regards,
Antonio