I've been running an IPN script (it's a PERL script that updates a .htpasswd file) from this credit card processing company for years and just yesterday it suddenly couldn't connect to my server and keeps getting connection time outs.

The error message shown on the credit card processor's control panel is: Unexpected Content Returned.

According to the credit card processor, it looks like the server does not allow us to access the script. They also claim that they do not have any problems with their other customers for reaching the scripts on their server and can see that the URL for the script is setup properly for my website.