EDIT: So, I got the Mystery Egg, returned to Lab, saved again, backed up save file again, and now it's importing fine...but I'd still like to know why it wouldn't let me before.
So, my Gen 2 Gold Version won't open when I try to open the .sav file. Never had this issue before and I've imported many Gen 2 sav's before.
This is a physical cartridge, by the way. I backed up the SAV with my cart dumper thing. I attached the photo of what happens. Other Gen 2 sav's are opening fine. All I did on this SAV was start a new game, get my starter, and walk to the first Pokemon Center available, then save the game.
Not sure why it backed the game up as "GLDAAUE" either.