I am using ADE 2.0 with OS 10.6.8 Snow Leopard with no problems, but I understand that earlier Mac operating systems, such as your 10.5.8, may operate OK with the earlier ADE 1.7.2. It doesn't show up on many current ADE web pages, but a search on Google should show up a link to the earlier download page. Good luck.
Thank you for information. I downloaded ADE 2.0 and it works.
Sent from my BlackBerry 10 smartphone on the TELUS network.