I am Running version 1.3.9F and have been for almost a year. I have been using paypal standard IPN with no errors.
I have not upgraded or added anything to the site and have been receiving orders all week. Today during the final step of processing an order I confirm the order and receive a screen in IE 8

This content cannot be displayed in a frame

To help protect the security of information you enter into this website, the publisher of this content does not allow it to be displayed in a frame.

I contacted paypal and they said:
If using frames, you will want to add target="paypal" in the <form action> tag of the HTML code to prevent our payment page from being displayed in a Frame

Does anyone know how to do what paypal requests above?

The site is BowEquipped.com

Foxfire says its an untrusted cert.