Safari downloads PHP author page instead of serving it.

I have noticed a strange thing has started happening with my site. When a user comes to the site using Safari and clicks on a link to load an author page. Safari will download the file and not load it on the screen. It will download a file with the HTML that should have been shown in the actual browser itself. All other browsers load the page with no problem. Only Safari on a Mac. Has anyone dealt with an issue like this?

First thing I thought of was the HTML headers which look correct. Besides its loading the same wordpress header on other pages without problems.