Not sure why this worked, but this is what I did. First, I erased the authorization for my new Adobe ID on my MacBook. Initially, was getting the "can't erase authorization, try again later" message, so I took advice from another thread and trashed the activation.dat file. I then authorized my MacBook for my old Adobe ID and then added my old books. Now all my books are showing up in ADE, both old and new, but under the wrong Adobe ID. I clicked on one of my new books and ADE automatically authorized my new ID, so now my MacBook is authorized for both my ID's and all my books are appearing as they should.
I now have another glitch. While my computer is saying it is now authorized for both my IDs, and all my books are appearing in ADE, I can open books associated with my old ID, but I can't open any books associated with my new ID. When I try to open one, it takes me through the computer authorization process again. I enter in the appropriate ID, even though my computer says it's already authorized, and my password and I get the message that the book is associated with a different ID. I even tried my old ID and got the same message. I trashed the activation.dat file again and went through the activation from scratch and still have the same problem. Does anyone have any ideas why this is happening?