I completely feel your pain. All my leagues are keeper or dynasty, and I just went through the exact same thing. Had 8 of 12 teams done, and had the same problems with a few of those teams, as I couldn't even get them to 25, because some players aren't in Yahoo's database yet.
I go back to finish today, and all my work is lost! I'm so %&^(% pissed off, I'd like to strangle something.
Funny, I just posted, and went down a few posts and saw yours. Misery loves company.
BTW.....I also emailed Yahoo about their changes this year sucking. And, got the same reply you did.