Thanks for your help. Yes, always create a backup before doing anything! That is a good advice.Good thing I did that, the upgrade failed a couple of times so I had to restore everything. I deleted the table 'osti_content'
and then it worked. I think I got a couple of emails with some errors
that I must have accidently deleted, but everything seems to work fine.
Piping didn't work until I changed pipe.php's file permission to 744 (I
guess it is safer than 755) - it has never worked with 644. Is it okay
to chmod to 744 and do you have any idea why I have to change file permission for that file every time?