I\'m using 5.1.41-3ubuntu12.10 for my MySQL version.
UPDATE profiledata SET aboutyou = \'$aboutyou\', quotes = \'$quotes\'
WHERE uid = \'$sess_uid\'
MySQL does have multi-table update support: http://dev.mysql.com/doc/refman/5.0/en/update.html.
UPDATE profiledata, profileprivacy
SET aboutYou = ..., aboutyouPrivacy = ...
WHERE (profiledata.uid = $sess_uid) OR (aboutyouPrivacy.uid = $sess_uid)
or something similar should do the trick.
You can use a join like this:
$query = "UPDATE profiledata t1
JOIN profileprivacy t2 ON (t1.uid = t2.uid)
SET t1.aboutyou = '$aboutyou',
t1.quotes = '$quotes',
t2.aboutyouPrivacy = '$aboutyouPrivacy',
t2.quotesPrivacy = '$quotesPrivacy'
WHERE t1.uid = '$sess_uid'";