[imp] success change password via "Passwd", but failure afterwards

[Nethub Online]

Hi all,

Since I am going to use new version of Horde to replace old one, so I do
lots of testing on it. So sorry that I have submited many post for the
problems, 
but I think it is standard to submit single post for each problem.

Horde Version: 5.1.1
Imp [Mail]: H5 (6.1.2)
Passwd Version: H5 (5.0.0)
PHP Version: 5.3.3

Passwd is using poppassd

After using Passwd to change password successfully, it seems IMP is still
using old password to do further operation such as checking email, setting
preference...etc. Hence everything is not working until I log out and log in
again.

Horde log:
2013-07-13T00:18:16+08:00 EMERG: HORDE [imp] Mail server denied
authentication. [pid 16349 on line 94 of
"/xxxxxxxxx/imp/lib/Imap/Exception.php"]


Can anyone else confirm this problem?