Theme Suddenly Causes White Screen in /wp-admin/

Hi,

I’ve got an install of 3.9.1 that’s been that way since early May I believe. My theme hasn’t changed other than a few minor styling things since April of 2013. Now suddenly today the theme is breaking the admin panel. If I force deactivate it through FTP or phpmyadmin I can get into admin and reactivate it, but then if I try to do anything else that involves saving changes, whether it’s a setting or a post the screen goes white and I can’t get back into it.

I’m also getting the following error when trying to login with a different browser while going to /wp-login/.
ERROR: Cookies are blocked due to unexpected output. For help, please see this documentation or try the support forums.

Now if I change my theme to say, Twenty Fourteen that error goes away and everything is fine. I’m absolutely baffled why all of a sudden, after no changes this is happening. Luckily the site itself looks fine with my theme, it’s just the admin so we can’t update it.

Aside from narrowing it down to the theme I’ve also done the following:

-disabled all plugins
-checked for spaces in wp-config and function.php files
-turned on Debug in wp-config (but I get absolutely no output whatsoever.)
-Reinstalled wordpress 3.9.1

At this point any ideas or tips would be greatly appreciated and I can supply any extra information that may be needed.

Thanks!