Let me first say that I am running on a shared linux server with HostGator.
My problem is I had this line of code in my .htaccess:
Header set Access-Control-Allow-Origin *
Which allowed cross-domain xhr requests. It was working find till my hosting provider told me to add this to get php 5.3 (which my program requires):
# Use PHP 5.3
Action application/x-hg-php53 /cgi-sys/php53
AddHandler application/x-hg-php53 .php
Now I can no longer make cross-domain xhr requests. Does anyone know why this no longer works? (I do get PHP 5.3 though)
** Update **
Well, it looks like it's something that's not my fault and something I can't fix. Here's the official response from HostGator Tech Support:
I've examined your site, the error logs, and the .htaccess directives, and unfortunately I've come to the conclusion that the "Header set Access-Control-Allow-Origin *" line is not compatible with our implementation of PHP 5.3 as found in our shared servers. I sincerely apologize for the inconvenience that this causes, but the way we implement and call PHP 5.3 (since 5.2 is the default and cannot be altered thanks to cPanel) apparently overrides the Header handling mechanism, making it not work correctly.