HTTP error on Adobe DRM Activator request

I am unable to open newly purchased ebooks with Digital Editions. Windows XP, SP2, firewall and anti-virus turned off. Not behind any firewall.

Adobe DRM Error
System: 7
State: 4
Class: 5
Code: 31
Message: Your Adobe software could not be activated. HTTP error on Adobe DRM Activator request. Adobe DRM Activator error (client code 31; HTTP code 555).
Fault location: 5

What are my alternatives? I am unable to open these books in Adobe Reader 7.0 or (of course) 8.1.

-- rk