We currently have a bookings system on the site that uses the IPN. We also have a couple of Paypal buttons for Paypal gift certificates.
When someone purchases the Paypal gift certificates the booking script receives the IPN and doesn't know what to do with the IPN and sends an error notice....
Is it possible to remove IPN for the Paypal gift certificate buttons in the advanced settings on the button? If so, how?
You can use the notify_url parameter in your HTML button code or general checkout forms for PayPal to override what's in the profile setting. So you should actually be able to leave IPN disabled in your profile, but then include the notify_url parameter in your button to go ahead and send it just for that one button (or any buttons that you include it with).
Alternatively, you could adjust your current IPN script to handle the different transaction types accordingly. IPN includes a txn_type parameter, so you could check that in your code and simply exit the script or do whatever you want with each individual transaction type.