Seems at some point /openx_dir/www/admin/plugins/RevMax/templates/paypal-button.php may have been overwritten, and might return a error such as.
"The link you have used to enter the PayPal system contains an incorrectly formatted item amount."
I believe this error to be assoiced with return url when set and no
rm= value set.
If you have encountered this error add at line 49 to paypal-button.php
echo "<input type='hidden' name='rm' value='2'>"; // don't remove unless you know what you're doing.
Or download the latest package from your download link, and upload new file to server.
