How to fix E_Auth_Bad_Device_Key or PKCS12 error

I've used my Nook numerous times at this regional ebook site but now, all of a sudden, I can no longer download to the Adobe Digital for xfer to my nook.  I've scanned all the faqs but haven't come across this error.  I did update to Adobe reader 3 or some such but no other changes that I know of.   Help?? Chuck