I finally had success downloading a library book from my public library. Here is what worked for me....
I de-authorized and re-authorized as per sjpt's instructions...(even though I had already done that several times with no previous success).
( I have the Adobe Digital Editions v2.0...Windows 7...Internet Explorer 9...Kobo Glo....Ontario Public Library: Overdrive. )
I then reset the factory settings on my Kobo Glo, but when I restarted it, I did so via the usb method instead of the wireless method which I had done before. I followed the prompts to re set up the Kobo Glo. I then connected the wireless under 'settings'on the Kobo. I also made sure all the settings were correct....the time was incorrect, so I corrected it. I checked the 'account' under 'settings' and saw that Adobe was not signed in, despite the fact that I was signed in on their website and I had re-authorized both the computer and the Kobo just previously.
With the Kobo connected to the computer with the usb cable and connected to manage files, I opened my Adobe Digital Editions and checked to make sure the authorizations were still there. The computer (click the' help'button to check )was authorized still, but the Kobo (click the button next to 'device' that shows your Kobo to check. Remember to click the kobo device line first.) was not authorized any longer. I authorized it...again.
Then I chose a library book I had previously downloaded to ADE, clicked and dragged it to the Kobo device line....saw that it downloaded....safely ejected the Kobo...and there it was on my Kobo home page!!!! Also, under 'accounts' in 'settings', Adobe was signed in.
Let's hope this is solved now.
FranTod, I know you have tried all this...so had I.... but this time it worked with a few subtle differences in the way I did it. I wanted to share this result, in case it will work for you too.
Good luck.