[horde] bug with login portal vs imp?

[fuxa_kos at unihost.cz]

When my users are logged to portal

Horde :: My Portal; https://.../services/portal/
from https://.../login.php

they get in IMP widget
Error
 User is not authorized for imp

and doesn't see mailbox. Other modules like turba (Address Book) works
fine! Type /imp/ to URL and got login screen again (for already loged
user).

After new login (under IMP), they see Inbox fine and when goes to
/services/portal/ - IMP widget and other portals widget works fine too.

Mail
Folder Unseen Total
Inbox  -  41

Looks like portal login doesn't share user auth with IMP.

What is wrong?

My version, all up2date
CentOS 5.6
Zend Server CE with PHP 5.3.5
Apache 2.2
Horde installed as
pear install horde/webmail
Horde database (Mysql) upgraded from previous version Horde 3.

regards Martin