Just updated to ADE 2.0, at the request of the program which said I would not be able to view my books unless I did so. Upon restart, the program would open, but trying to open existing eBooks would get me the "spinning wheel" and necessitate a force quit of the program. All the book icons had an exclamation point in the upper right hand corner.
I had upgraded to Adobe Reader Version 8.1.0 prior to this, whenever it was released.
I am running Mac OS X Version 10.4.10, 1 GHz PowerPC G4, 768 MB SDRAM.