Hey, were you ever able to resolve this problem? I'm having the same problem.
I checked the following six registry entries
The "default" values all point to the right executable like this: "C:\Program Files\Adobe\Adobe Digital Editions 3.0\digitaleditions.exe" "%1"
Thanks for your attention,
I'm having the same problem - can't associate acsm with ADE - just with Adobe Reader.
Can't seem to find a solution anywhere here.