Looked for 45P last night and it wasn't there.  Today a friend commented about its nearness to galaxies and recalled that my data put it on top of a bright galaxy.  Turns out that with the same Dec 2015 version of Guide9 and the same full MPCORB.dat file,  the Guide9 on the office computer has it at one location, and at a slightly different location on the observatory computer.

This afternoon I checked and all the basic Guide setup/location/time settings seem to be identical and the data file is copied from office to observatory.  For 21:30 EST Feb 20 the observatory positioned 45P at 12 19 52.7 / 29 35 13 while the office positioned at 12 17 31.3 / 30 08 16.  Then to confuse things further,  while checking the observatory I pulled down a position of 12 14 46 / 30 46 22 using the EXTRAS/ASTEROID COMET OPTIONS/ADD MPC COMETS ASTEROIDS.  The USE MPCORB box in this option is checked.

I'm mostly doing asteroid astrometry and occasionally (10% of the time?) when I try for a comet it's not there.  This is probably what's happening.   But exactly what is happening here?  Suggestions solicited...

Pete Peterson  I15