This morning I just discovered the Bluefire reader app. It works well. I would say you need to read the directions first, and have to go through Adobe id but it works great on my iPod 2nd Gen with OS 4.2. and iMac with OS 10.5
here's the link to the website, which will also link you to the App store.
Be sure to read the directions. You will also need to know where Adobe Digital Editions places the epub ebook file ( Digital Editions folder in the Documents folder)
Hope this solves it.
PS: I contacted iFlow Reader, another great reader app, and they also have solved the problem and have a revision waiting for apple to approve the update. This one was recommended by Adobe, but it's not quite ready. Both of these apps are free!