Virtualbox cannot load the Qt platform plugin "xcb" on Crunchbang Waldorf

I am running Crunchbang Linux (Waldorf), a distribution based on Debian Wheezy. I downloaded the most recent virtualbox from here https://www.virtualbox.org/wiki/Linux_Downloads , which is VirtualBox 5.1 for Linux. I run the command sudo dpkg -i virtualbox-5.1_5.1.0-108711~Debian~wheezy_i386.deb And here is the entire output: (Reading database ... 196982 files and directories currently installed.) Unpacking virtualbox-5.1 (from .../virtualbox-5.1_5.1.0-108711~Debian~wheezy_i386.deb) ... Setting up virtualbox-5.1 (5.1.0-108711~Debian~wheezy) ... addgroup: The group `vboxusers' already exists as a system group. Exiting. Processing triggers for hicolor-icon-theme ... Processing triggers for shared-mime-info ... Processing triggers for desktop-file-utils ... When I enter the command virtualbox I get the following error message: Qt FATAL: This application failed to start because it could not find or load the Qt platform plugin "xcb". Available platform plugins are: xcb. Reinstalling the application may fix this problem. I installed the package xcb but no change. Any suggestions?