Theme key "ljxp_user_info" not found.

No idea where this can come from :(

It comes from

function ljxp_user_view($account, $view_mode, $langcode) {
global $user;
if (user_access('can crosspost to livejournal', $account) && ($user->uid == $account->uid || user_access('administer site configuration'))) {
$ljxp = ljxp_load_settings($account->uid);
if (!$ljxp->active) {
$output = t('Not active');
}
else {
$output = theme('ljxp_user_info', $ljxp, $account);
}
return array(t('Livejournal Crossposting') => array(array('value' => $output)));
}
}

It expects theme to have ljxp_user_info. Any idea what shall be there?

I see the function theme_ljxp_user_info($ljxp, $account) declared but it is definately not called.

And I see no information about LiveJournal cross-posting status in the user view (it looks like, this is the purpose of this function to be called).