When you quit the window manager, you'll also quit X. You might try it without the backgrounding just to see what happens.
"Debian GNU/Linux: Guide to Installation and Usage"
John Goerzen and Ossama Othman
Lucetta, shading her eyes from the glow of the fire, saw two gleaming disks of light shining in the blackness of the backgrounding forest.
"Stranded in Arcady"
Francis Lynde