Cannot open the ebook

I have already successfully downloaded the Digital Editions to my first iPad. Then, I downloaded an ebook which does have appeared in the Digital Editions. However, every time I clicked the ebook, either the Digital Editions turned off automatically or the ebook showed the sign of loading. At the initial, I thought there were something wrong with my first iPad. So, I went through the same processes again using my second iPad. The things keep happening again and again. The other ebooks in the Digital Editions are fine, no such problems appear.

In short, the ebook I want is already in the Digital Editions. I just cannot open and read it.

My Adobe Digital Editions is Version 4.5.11.187353

On top, I have chosen "authorised". Also, I have tried few times removing the ebook and downloaded again and again. Still can't open it.

Please help.