I was checking the Joomla! 3.0.0_Alpha1 version and got an error after installing one of extension that shows Directory separator constant DS error. So if you get such error for any of your extension try this code

if(!defined('DS')){
    define('DS',DIRECTORY_SEPARATOR);
}

May be making a system plugin can solve this problem. I developed one 😛

[download id=”35″]

BTW, we develop custom joomla extension at codeboxr.com