[David4069]

Make sure there is an entry for the star size, color, etc combination you are trying to use in the SectType.txt file. I had the same problem, so I set the stellar variables in SystemTypes.txt to any. It seems that while there is an entry in SectType.txt for all planet size, composition and atmosphere combinations, not all possible stellar combinations have an entry. For example:
(from SectType.txt)
Physical Type := Star
Picture Num := 227
Description := A very ordinary yellow star.
Star Size := Medium
Star Age := Average
Star Color := Yellow
Star Luminosity := Average
This is the entry for a medium-sized, average aged yellow star that has an average luminosity. If you try to reference a huge, young, yellow, super-bright star in SystemTypes.txt, you will get the same error, most likely because it can't determine which Picture Num to use, because that combination doesn't have an entry in SectType.txt.

[This message has been edited by David4069 (edited 21 December 2000).]