lose of windows upper part

[unbewusst]

On Linux Mint 13 "Maya" XFCE 64 bits, i do not have any more the upper part of the windows.
This Linux version had been installed 3 days ago.
After that i have installed :
Dropbox
Opera
zsh
xclip
smbfs
xscreensaver-gl
openssh-server
preload
xserver-xorg-input-synaptics
expect-dev
sshfs

I do not remember when this bugg (?) arroses.
May be it's only a mistake of me playing with parameters ?

[mephisto]

Try this, open terminal
type xfwm4
that should start the windows manager... see what happens, if the window looks OK again go to menu [Settings -> Session and Startup] and save the current xfwm4 session.
Reboot.
That fixed it for me.
Good luck.