I keep getting emails from PayPal asking me to fix the URL that notifications are sent to

The URL is http://rimbitforum.com/index.php?app=nexus&module=payments&section=receive&validate=paypal which throws up an error 2S100/6

I have nexus... The site is URL friendly, but I can figure out what I need to do to correct this situation

Replies most welcome

Are you on IPS 4? It's gone in IPS4, a legacy bridge is coming soon though.