I can't change user password.

[akong]

I have use poppassd to change user password.I have test change password use telnet.It's can change password.But when I use roundcube 1.0.2 password plugins and choose poppassd to change it.It's will show Old password incorrect.But I can use old password to login roundcube webmail.What is this problem?
My system is Centos 5.10
Roundcube 1.0.2 via yum installed
poppassd version is 1.8.5-3
How to fix it?