I'm using 6.3.6 of the plugin - just upgraded on a site a couple of days ago. I'm using a bit of code for a custom widget I wrote (I got the code a while back from the dev's website, I think).
anyway, the line the error is:
Call to a member function shortcode() on a non-object in wp-content/themes/theme/inc/widgets.php on line 1009
and it refers to this line in my code:
echo $GLOBALS['theme_my_login']->shortcode( $args );
but apparently "shortcode" is no longer supported? Was this replaced by something? I looked in teh changelog, but don't see any mention of it.