Classifieds gives me a 500 error

Hi, I backupped and moved my site with a working Classifieds plugin to a new hoster. I used the original backupfile and the site is not working anymore. When I disable the Classifieds plugin (renaming the folder in wp-content/plugins/) it works.

I found out that my new hoster is using PHP Version 5.3.26, the old hoster has PHP 5.2.x

How can I get the plugin to work again in an 5.3 environment?