I think you've hit a 'known issue' in the MS DPAPI

HCL Notes/Domino 8.5 Forum (includes Notes Traveler)

Subject:

The Notes Shared Login feature uses the MS Data Protection API (DPAPI) to encrypt/decrypt information which allows access to a notes id. The error from your posting below (0x8009000B) is defined as "Key not valid for use in specified state." and is being returned by a DPAPI function. You mentioned above that your system was added to a Windows Domain. You've likely run into the following issue:

You Cannot Access DPAPI Confidential Information After Joining or Disjoining a Domain
If you have joined a stand-alone computer to a domain and you have lost access to DPAPI data, you can restore access by logging on as the local user. To log on as a local user on a domain-joined computer, click the local computer's name in the dropdown box in the Logon dialog box, and then enter your local user name and password.

If you have disjoined a computer from a domain, you must rejoin the domain and then log on as the same domain user to regain access to your files.

(from http://support.microsoft.com/kb/309408#12)

Please try the recommended steps above to see if that resolves your issue.

Feedback response number DJAG7XJK54 created by ~Wei Kikigon on 11/06/2009