Hi Sean,
Open gpedit.msc (Start -> Run -> gpedit.msc -> click OK). Under Computer
Configuration drill down under Windows Settings -> Security Settings ->
Local Policies -> Security Options.
Here look for policy: Interactive Logon: Number of previous logons to
cache... Set this number to 0 (default is 10).
Restart the computer and check if the cache was cleared (if you can logon
with cached credentials)...
Mike