Javascript not Working Properly With Cox

I use my email on Cox.net. Yesterday I started having issues with their webmail. When I log in the page doesn't appear correctly. In my message preview pane it overlaps another item. So I contacted Cox about the issue and I've tried to clear cache and cookies on my computer, make the security level in Java high instead of very high, uninstall Firefox and reinstall it, restart Firefox in safe mode, change the advanced Javascript settings in Firefox, uninstall Java and reinstall it, I've restarted my computer after the installations, and clear Java cache. Yet in Internet Explorer and Google Chrome it works perfectly fine. Firefox displays it correctly on my mom's computer. What haven't I done because apparently it's only doing this on my laptop?