Hello,
I also went into the same problems above when testing Live with Paypal.
I had also modified the
define('MODULE_PAYMENT_PAYPAL_IPN_TEXT_TITLE', 'PayPal (Credit Card / Debit)');
to
define('MODULE_PAYMENT_PAYPAL_IPN_TEXT_TITLE', 'PayPal');
to reflect the Paypal language in french.
I had the problem then I changed back to :
define('MODULE_PAYMENT_PAYPAL_IPN_TEXT_TITLE', 'PayPal (Credit Card / Debit)');
as you described above and it worked fine.
But I'd like to have for example 'Paypal' alone.
Who ever try to change the value of this variable to reflect the website front-office language ? Or is there a fix for that ?
Again, thanks for the fix above, it really helped, combined with Mushroom's fix paypal_ipn.php file.

Patrick