FileReference throws Error on domain with htpasswd

I’d never used FileReference on a domain protected by htaccess and htpasswd. I’m getting I/O and Stream errors when my SWF is hitting those PHP scripts. I know I can host the PHP on an unprotected domain, but I’d prefer not to do that.

Is there a Security item I can use to get past the Errors, or maybe something in the PHP?

Thanks.