problem using IE7 together with an automated login to a website

Hello,

we have the following problem using IE7 together with an automated
(integrated) login to a website.

after changing the windows-password the windows-login works correctly with
the new password, however we have a problem with a login to a website
(citrix application portal)

The moment the user starts the website his windows-account is locked-out.
His usually happens only if a wrong password is used.

Now we think that the problem might be that the IE7 tries to send the old
(chached ?) password to the website - and this results in an account
lock-out.

Is it possible to prevent that IE sends (old) passwords to a website?

deleting temp. files and cookies didn't work, but even if it would have
worked this would not be a good option because we have many users who will
change their passwords frequently in future.

thank you
Heinz