Web admin console immediate disconnects with external authentication

The web admin console works just great with internal authentication. But after switching to a simple external authentication script, the console asks for my credentials, validates them (my script returns a positive response), but then the browser gets hard disconnected from ejabberd.

The log file contains the following:

=INFO REPORT==== 2010-06-07 02:30:58 ===
I(<0.443.0>:ejabberd_listener:232) : (#Port<0.418>) Accepted connection {{127,0,0,1},61780} -> {{127,0,0,1},5280}

=INFO REPORT==== 2010-06-07 02:30:58 ===
D(<0.453.0>:ejabberd_http:135) : S: [{["captcha"],ejabberd_captcha},
{["admin"],ejabberd_web_admin},
{["http-bind"],mod_http_bind},
{["http-poll"],ejabberd_http_poll}]

=INFO REPORT==== 2010-06-07 02:30:58 ===
I(<0.453.0>:ejabberd_http:137) : started: {gen_tcp,#Port<0.418>}

=INFO REPORT==== 2010-06-07 02:30:58 ===
D(<0.453.0>:ejabberd_http:254) : (#Port<0.418>) http query: 'GET' /admin/

=INFO REPORT==== 2010-06-07 02:30:58 ===
D(<0.453.0>:ejabberd_http:323) : ["admin"] matches ["admin"]

And stops there.

The script authenticates XMPP clients just fine.

Any ideas? Thanks!