I wanted to upgrade from player 4.5 to 4.6 and for this I've replaced the files 'swfobject.js' and 'player.swf' on my web site as I did in the past when newer versions were released. The two files are located in a subfolder called 'embed'.
But this time the new player doesn't work. I get a JavaScript error 'SWFObject not defined', but the JavaScript code is still the same as before, according to the examples on this site. When I upload the older files of player 4.5 everything works fine again.
To fix the error by myself I've tried to run the new player.swf together with the swfobject.js of version 4.5, but this doesn't work, too. In this case the player doesn't find the video file.

Check the version of swfobject.js that you are using. Open it with a text editor, the version will be in the first few lines.
The error message "SWFObject..." means that you need v1.5.
You can get SWFObject v1.5 here http://blog.deconcept.com/swfobject/#download