I've install zoneminder in ubuntu precise 12.04 at first it was working ok, but someday stopped working, maybe there is an update that make it stop working.
I have usb cameras and they were working ok, know they are like scrambled I cant see nothing.
zmu -d /dev/video0 -q -v
Error, failed to enumerate standard 0: Success
found solution !! $ENV{LD_PRELOAD} = ‘/usr/lib/libv4l/v4l2convert.so’; that works :=)