I've had the same problem. I always save the map in increments now. This way when the map fails to load I can always try a previous version of that map and see if that works. Your map will not load, so you can either go back to a previous save of it or just delete it and start over. It seems that adding planets and asteroids after the map is finished will cause some sort of problem. You have probably made a few deletions or have added to many asteroids on the map.

One question, how many asteroids should I add?

Thanks Xrati,

I was limiting the asteroids to 4 per system. I did change some of the stars and planets after running the randomizer and did not save the map enough while making all of the changes. Given what you said above I think that is why my map wasn't loading. I did have one more question. I do know that planets are limited to five per system, but is there a good rule of thumb regarding the amount of stars that should be placed? Something like 1.5 to 2 per sector? Thank you for your advice.