Error when open Ninja Xplorer

I just recently installed Ninja Xplorer in Joomla 2.5. When I try to open the component, I am getting the following error message:
Fatal error: Call to undefined method JAccess::get_group_id() in /home..../administrator/components/com_ninjaxplorer/admin.ninjaxplorer.php on line 81.

Could somebody help to fix it?
Thanks.

07 Mar 12

Hi aolga,

This is because NinjaXplorer isn't compatible with Joomla 2.5. This is shown on the NinjaXplorer page on the Joomla Extensions Directory, as well as on the NinjaXplorer page on our website.

Kind regards,
Mark