Hmmm, this thread was actually helpful. I'm not used to that. Thanks everyone.
Was having the no stars or planets spawned/insta-defeat issue while trying out my GF3 created maps. Was saving it in the custom maps a.k.a. wrong folder. Put it in with the game galaxy folder and problem solved. Seems to me that if a map doesn't show up in a list or load up, then it's simply a "wrong folder" / "listing it in some file" issue.
BTW if anyone is making a list of what set up combos are working and what's not: Vista 64-bit, SP1, .net 3.5, Sins 1.15, Forge Tools 3 (downloaded yesterday, the 28th)... Everything installed to default directories, forge tools are just on my desktop. Everything loads up just fine.