Hmm, this is a strange now. I do all my development on 5 but I installed 4.1.22 and the query is indeed a valid one. Try this, open includes\functions_vbsfs.php, go to line 71 and change
$sql = "SELECT DATEDIFF(NOW(), '" . $lastseen . "') AS DAYS;";
to
$sql = "SELECT DATEDIFF(NOW(), '" . $lastseen . "') AS DAYS";
Notice the ; removed from before the last "
Can you PM me your exact version of mySQL, PHP and Apache that youre using on the forum that gives you this error, your server locale (US, Japan, French etc) so that I can look at it a bit more
I tried to register on your forum but your NoSpam questions/answers are wrong. 8+8-3 = 13 but not according to your forum