Can't download by double-clicking ACSM file

I have a couple of ACSM files that are on my local drive (due to a browser problem).  When I double-click on one, it launches Digital Editions, but it doesn't download the epub - nothing happens at all.  I can make the download happen by doing File -> Open inside Digital Editions.

In addition, it was possible in earlier versions to download from the command-line by running:

digitaleditions.exe  URLLink.12345.acsm

but that no longer works.

I'm running DE 4.5.10.186048 on Windows 7

Any suggestions??

Thanks!

Dan