Security Certificate
If you have received this error message:
"Why?"
With either Windows XP or Vista, if the Windows log-on password is either reset or removed on a computer (password changes work fine), the user of that computer will find that any certificate which was created prior to the password change will no longer work. As a result, the ID Vault credential store, which was encrypted using that certificate, is no longer accessible. That is because the certificate that ID vault used to encrypt the file is no longer tied to the Windows password which was in place when the file was created. Any application which uses a security certificate is subject to this since any application security certificate is tied to the Windows log-on information/Password. The only solution is to recreate the certificate. Unfortunately, this also means recreating any saved sites, and the user PIN verification number since that information is tied to the security certificate. Where ID Vault is concerned, the corrupted certificate must be deleted and a new one created.
For more information, see this Microsoft Library entry:
http://support.microsoft.com/kb/290260/.