Adobe Digital Editions crashes all the time-

I'm trying to use it with Netgalley on my iMac G5. When I download a book and try to  open it in Adobe Digital Editions, I get the spinning beachball of death! Twice in a row now, it has simply frozen on me, and I've had to send error reports to Apple. I am running Leopard and the machine, though old, is generally pretty stable. Do I need to update Adobe Digital Editions or perhaps get a different version for a Mac PPC? I don't really understand this - it used to work fine on this machine!

Thanks. Please let me know if this isn't clear, or if I can give you any more information that might help to solve the problem. I'm just trying to get a Netgalley ebook onto my Sony pocket reader via Digital Editions.