Hi,
I also upgraded to Windows 8.1 and here it works like a charm.
From your User-Agent String I can tell that you are using Chrome,
which as far as I remember, has its own flash support built in. Maybe this is the reason for the issues you are experiencing.
Can you try it out with a different browser, e.g. Firefox?
Best regards
http://GayRoyal.com
Mozilla/5.0 (Windows NT 6.3; rv:25.0) Gecko/20100101 Firefox/25.0