Closed Digital Edition.
Rename the My Digital Edition folder under your Documents to My Digital Edition.old.
Restart the software and try to download the eBook again.
I am having the same issues, now trying with ADE 4.5.8...no luck, using an Ontario, Canada library, have had some success in the past, the odd file seemed 'corrupted'...now, nothing. The library part of the download is working properly, but when I click on the .acsm file, ADE stalls, and finally I get (Not Responding) message....and this...has become very consistent!
I have the same issue. I'm running version 126.96.36.199862. It used to work when borrowing ACSM files from our public library (in Canada as well). The last 3 books over the past week downloaded and created stubs in ADE, but ADE crashes before completing. When I restart ADE I see the stubs, but if I click Read on any of them ADE crashes again, and again.
I tried removing the stubs, but they keep coming back like ghosts. I renamed the My Digital Edition folder, as suggested above by Nanaky, all other books disappear, but the ghost stubs of the last 3 borrowed books keep coming back.
I uninstalled and cleaned the registry (Windows 10) best I could, restarted and reinstalled, but the ghosts stubs remain and borrowing more books keep crashing ADE. I don't know what else I can do at this point. I am about to give up on Adobe Digital Edition as unreliable.