Hi Ben,

I'd recommend e-mailing me the files 'comets.dat' and 'startup.mar'
from your Guide folder. Quite a few comet/asteroid-related calculations
are done in 'lunar.dll', and my guess would be that some odd sort of
data is being passed to it and resulting in a crash. (I say this
largely because you mention just having updated comets.)

Given the comet file and the settings stored in 'startup.mar', I've
some chance of puzzling out the problem.

Another thing to try: as Guide is starting up, hit the space bar
(to stop it from drawing). Go into Display... Data Shown and turn off
comets and asteroids. If Guide now runs correctly, then I'm right in
thinking that it's something related to those objects (and you'll have
something that works, albeit missing some very important objects,
until I figure out where the problem lies). You might then give a try
to turning on asteroids or comets, to determine if either can be
turned on without causing disaster.

-- Bill