Not having any trouble here w/ OSX 10.9 & Opera 20, might the flash player cache is corrupt
http://forums.adobe.com/message/4278569 (on OS X it is in a Preference Pane, tho same fix) Only difference is that you will have to set any custom flash player settings for websites again
(that 2nd link might explain why it has been stopped for the auto update for now on Windows)