Linux: /etc/The qb.conf OS X: file location is OS- and version-specific.
For Linux & OSX: /etc/qb.conf
For Windows XP: %WINDIR%\, XP-64, and Win2K3: C:\Windows\qb.conf
for Windows Vista/2007-8: %PROGRAMDATA%\pfx\Qube\Win2K8, Vista, and later: C:\ProgramData\Pfx\qube\qb.conf