wp_get_current_user()

I'm creating a simple plugin, and need to call wp_get_current_user();

That function is in plugables.php which is loaded after all the plugins, so I get the 'call to undefined function' error.

On searching various wp forums 'init' is mentioned, and also the fact that BuddyPress has got round this problem.

I was wondering if anyone on the buddypress team could shed some light for me?