[Plugin: Sidebar Login] get_userdatabylogin is deprecated

get_userdatabylogin() is deprecated since version 3.3.
Use get_user_by(‘login’) instead.

Change
if ( $user = get_userdatabylogin($user_name) )
to`
if ( $user = get_user_by('login',$user_name) )

http://ww.wp.xz.cn/extend/plugins/sidebar-login/