In order to fix the problem you can try following.
Solution ) Delete following folder from your computer.
C:\Documents and Settings\UserName\My Documents\My Digital Editions\Restore
Delete Restore folder and then open book again.
HD:/Users/UserName/Digital Edittions/Restore (If you are using MAC)
Solution 2) Download the file first once downloaded right click on the file and choose Open with>>Adobe Digital Editions.
I hope this will help you!!!