Okay, I'm totally confused and dumbfounded. I've tried almost everything to resolve this issue. Its definitely an AJAX problem of some sort.
When clicking "Log In", the URL changes to "#prettyPhoto-login[ajax]/0/" - #prettyPhoto is obviously 'okay', but I don't understand why -login[ajax]/0/ is popping up. I have not touched the wp-login.php file.
It is NOT a theme problem. Its something internal. I deactivated my main theme, used WP's basic theme, and same problem.
Some browsers (Google Chrome) will still allow me to log in. But if I tried via Safari, it will log me in and then when I click Dashboard, it will log me back out.
Once again, I have not touched the wp-login.php file. I even redownloaded the wp-login.php file and reuploaded it to my server. Same results.
I have also tried deactivating plugins, menus to no avail. This is my last resort.