Bought and installed adsmanager extension for adsmanager 2.5 and artio version 3.2.9.

Everything works great except the module adsmanager menu

gives the following error

Fatal error: Call to undefined function: array_diff_key() in /home/sitename/components/com_sef/joomsef.php on line 598

It only happens when I try click on the categories. The other links on the menu work fine.

Can you give me an idea of how to fix.

So far I have un-installed and re-installed the menu module, cleared the cache but not luck.