6
if u do it the way i do it.. it shouldn't
what i did when i upgraded was to upload each file individually.. but b4 doing so, rename the file ur overwriting.. ie..
if u have to overwrite userinfo.php then rename userinfo.php to userinfo-old.php
do that for all the files ur overwriting.. then if anything shud go wrong, all u have to do is just change the file names back again and u have ur previous version..
if it involves a MySQL upgrade, then do a full dump of your database b4 hand, then upgrade the database.. again if any problems do arise, u got the backup to fully restore it..