Error when installing psa-qmail on ubuntu

[xxbartosxx]

Hi I get this error when I try to install Plesk 8:

Unpacking psa-qmail (from .../psa-qmail_1.03-ubuntu5.10.build80060428.20_i386.deb) ...
 Checking for the system groups and users necessary for Qmail...
 Checking for the group 'qmail'...
 Trying to add group 'qmail'... done

 Checking for the group 'nofiles'...
 Trying to add group 'nofiles'... done

 Checking for the user 'alias'...
 Trying to add user 'alias'... done

 Checking for the user 'qmaild'...
 Trying to add user 'qmaild'... done

 Checking for the user 'qmaill'...
 Trying to add user 'qmaill'... done

 Checking for the user 'qmailp'...
 Trying to add user 'qmailp'... done

 Checking for the user 'qmailq'...
 Trying to add user 'qmailq'... done

 Checking for the user 'qmailr'...
 Trying to add user 'qmailr'... done

 Checking for the user 'qmails'...
 Trying to add user 'qmails'... done

 Checking for the group 'popuser'...
 Trying to add group 'popuser'... done

 Checking for the user 'popuser'...

ERROR: It seems there is a user with UID=110
       in this system, but  needs the same UID
       for its operation.
       Unfortunately, this situation has not yet been
       resolved.
       Please, visit  for assistance.

Exiting...

dpkg: error processing /var/cache/apt/archives/psa-qmail_1.03-ubuntu5.10.build80060428.20_i386.deb (--unpack):
 subprocess pre-installation script returned error exit status 1

Pls help me