In some cases users in an Active Directory environment may see repeated lockouts after a recent password change. This is commonly associated with forgetting their new password, forgetting that they are logged onto another machine or server somewhere, or their old credentials are cached.
If after you have rebooted the machine, checked domain logs to try to figure out where accounts may be logged in, deleted Temporary Internet Files and you are at your whits end, cached credentials may likely be your culprit.
On your affected machine, run the blow command and delete any cached credentials that appear. This would especially be relevant if you are using a Proxy server.
rundll32.exe keymgr.dll, KRShowKeyMgr
John "Mike" Wright