flash player not working

I just installed Ubuntu. Do not know much about programming. Noticed that Firefox does not open Flash content (it only displays the "play" arrow) which in case of having flash navigation buttons is not very practical. However, when attempting to play content on some web sites (www.atptennis.com) nothing happens. It just freezes up.
Also, windows media files can not be played at http://wwitv.com for example.
Can someone help me with these issues, please?
p.s.: I reinstalled flash player and the same thing is happening. Funny thing about it is that some content plays ok (like you-tube), but some other does not. Would this help: this morning I installed Kaffeine and got a message of sort: "...codecs missing, some of windows media, real player and flash content will not play correctly..." Would this have anything to do with my problem (I do have problem playing all three occasionaly)?
Thanks.