User can't send any e-mail messages

[Carlos Ruesga]

Hi.. this is kind of weird.. I have an user that can't
send any messages, and when she try, she get's the
following:

"Your certificates are invalid for this e-mail address.
They may have expired, or the policy you are using may
not support the certificates you have."

She's using Outlook 2002, and there aren't any policies
in the domain..

Thanks in advanced