There are several things you can check... (1)update the printer driver, (2)add more ram to the computer (if it seems to be swapping during printing), (3)disable print spooling on the local machine.
I really don't think it is far fetched for the guy to turn off the machine nightly though... if that solves the problem.
HTH
Wayne
Wayne Myers, MCSD
Senior Consultant
Forte' Incorporated
"The only things you can take to heaven are those which you give away" Author Unknown