Well, I didn't realize when I wrote 1.3 that plugin_dir_url was not introduced in WP until v2.8.
I believe I will deal with this the lazy developer's way: emObA 1.3 requires WP2.8.
If you don't want to upgrade WP and you know a tiny bit of PHP, you could patch emoba.php around line 51, in the code
/****
Place the css in the head:
****/
function emoba_includes(){
wp_enqueue_style( 'emoba_style', plugin_dir_url(__FILE__) . 'emoba_style.css');
}
add_action('init','emoba_includes');
by replacing plugin_dir_url() with (I think -- not sure of the final slash)
'/wp_content/plugins/emoba_dir/'
where emoba_dir is the name of the folder emoba is in.