Ok, two separate issues but here, but fixed the same way. First up is Windows Update reporting:

Windows could not search for new updates Error(s) found: Code 80092026

Then un-related to Windows Update, a code-signing certificate issued from an internal certificate authority, reporting:

The cryptographic operation failed due to a local security option setting


Both issues fixed by deleting the following registry key:


I’m unsure of what the cause is, presumably it’s got something to do with the way Windows Vista handles certificate revocation and status checking.