user auth = 'imp but cannot login

[Mac Table]

hello,

when i edit registry.php, and uncomment the following:
$this->registry['auth']['login'] = 'imp' ;
it cannot show the horde login page, but if I comment
this line, I could see login page and then login

and also, I never go to imp/login.php successfully.

please show some advise/tips, but this problem occur,
thx.

my platform is 
debian 2.2
apache Apache1.3.23
php 4.1.2 with pear-4.1.0 which download from horde. 
php with imap, mysql gettext and ldap support
horde 2.0
imp 3.0

I have checked http://mydomain.com/horde/test.php
it shows everything ok and supports, session function
is also ok. (when i reload the test.php the session
no. can increase)


__________________________________________________
Do You Yahoo!?
Yahoo! Tax Center - online filing with TurboTax
http://taxes.yahoo.com/