I ended up doing an archive install back to 10.5.5, but this didn't solve the issue. So, it's not a 10.5.6 issue. I did a clean install to an external drive and it was going into sleep. I removed hacks and other programs that seemed they might be suspect. Finally I began to suspect Mozy and did a little search. I came up with this piece
https://forums.macrumors.com/threads/596222/ and after uninstalling Mozy the problem is gone. The reason I didn't suspect it sooner is that I did a safe boot and it still wasn't going into sleep, nor was it going into sleep from the login screen, which made me think it wasn't Mozy. I can't rest if my Macbook can't sleep!!!