I don't know what I did, but it seems that most of my programs are now using some poor old window design:
But for example nautilus doesn't have this problem :
Would anyone know what this is due to?
EDIT: Here are the result of the suggested commands:
kenny@Computer:~$ ls /usr/share/themes
AgingGorilla Atlanta Crux Emacs HighContrast Radiance Simple
Ambiance Bright Default Esco Metabox Raleigh
kenny@Computer:~$ ls ~/.themes
ls: cannot access /home/kenny/.themes: No such file or directory
kenny@Computer:~$