I have had a lot of experience with building PayPal IPN scripts. Rather than using tool which creates it for you, I would strongly recommend that you build it yourself using PHP and MySQL.
It is very easy to create a PayPal IPN script, and in-fact, there is a lot of documentation on the PayPal website itself. Here are some links which may help.
PayPal’s pre-made IPN script: Click Here
Information about IPN : Click Here
IPN PDF Guide: Click Here
If you do not understand the system, I would not recommend including an IPN script into your project as there may be security issues.
If you need further help, please do not hesitate to contact me.
Make sure you are connecting to your Database also. You may want to try the mysql_error() function at the end of the MySQL query.