Digital Editions could not connect to the activation server.

I know many people have discussed this before and I have tried all their solutions (I think ).

OS: Vista
ADE 4

Up till the 16/06.15 I had no problem borrowing books from my public library for at least a year. I can't think of anything which has changed apart from the date.
Today (20/06/15) I get the message, "Digital Editions could not connect to the activation server. Please make sure you are connected to the internet."

• I verified I was connected to the internet
• I rebooted
• I made sure I was not using any proxies, VPN, etc
• I verified my only firewall (ZoneAlarm) was allowing traffic to and from ADE
• I turned off my firewall
• I turned off my anti-virus (AVG)
• I verified with Task Manager that no other stray security processes were running
• I started ADE as Admin (suggested somewhere)
• I unregistered and failed to re-register my desktop computer with ADE - same fault
• I uninstalled ADE and reinstalled it
• I tried downloading the link for the book, then opening it in ADE
• I tried borrowing the book with my netbook (Windows 7), which worked , but of limited use to me.

OK, I'm stuck for the next idea. I'm limited by the license terms about how inquisitive I can get, (and I can't justify the time.)
Bright ideas anybody? Everything worked fine until today.