Joomla site transfering: Fatal error: Cannot redeclare class

[luitos]

Good morning to all.
I would like to transfer my joomla site from a domain name to an other (in the same ISP), where Phoca Guestbook and Phoca Gallery worked well.
I downloaded my site joomla files to my local PC.
I exported my MySql database to my local PC, too.
I changed all refereces to the old domain name with the new ( in configuration.php, in joomla files and in database)
I imported the data in the new database and I uploaded joomla files into the new domain directory.
Well, everything works fine, including Phoca Gallery, but not Phoca Guest.
When I click on Phoca Guest I get the following error:
Fatal error: Cannot redeclare class HTMLPurifier_AttrDef_CSS_BackgroundPosition in /home/san2124/domains/santuariodivalverde.it/public_html/ipersito/components/com_phocaguestbook/assets/library/HTMLPurifier/AttrDef/CSS/BackgroundPosition.php on line 128
What can I do to solve this problem ?
Do I have to do a fresh install of joomla and reinstall all of its components separately ?
Thanks in advance to all those who will want to give me a help.

[luitos]

Solved !!!
I have simply updated the Phoca Guestbook from joomla administrator panel.
Now all functioning.
Thanks at all.

[Benno]

Ok.

Kind regards,
Benno