On my linux machine I use vmware workstation 7.0.1 to run several windows machines. In each I use virtual printing to let the printers I configured on my host machine appear as local printers, without the need to share them throught samba or to configure them on each single vm.
From time to time (after upgrades) my virtual printer ceases to work: when I print from the vm the job fails and in my host machine I get an error from cups "stopping job because the scheduler could not execute a filter"
This seems to be caused by the filter
wich is incorrectly set to permissions "-rwsr-xr-x" instead of 555 "-r-xr-xr-x" as all the others.
to fix the problem, just set the permissions to 555
sudo chmod 555 /usr/lib/cups/filter/thnucups