[horde] horde auth suceeds, imp auth fails, user thinks he's not logged in

[amy.rich@tufts.edu]

We're using hordeauth to log our uses into imp.  If the IMAP server is down
for some reason, the login to horde (via LDAP) succeeds, but the login to IMAP
fails.  Unfortunately, the screen that appears is misleading because it says
"Login failed."  and presents the user with the Username/Password/language
options.  This is dangerous for us since users may not realize that they have
not been logged out of horde.  If a second user inputs his/her information at
this subsequent login screen the result is person A's attributes with person
B's mail.

Is there any way to _force_ a horde logout if the imp login fails?