Hi. My first guess is to update Flash.
http://get.adobe.com/flashplayer/If your system slows down, after installing, this is a known issue, please post here for help. It shouldn't though and can easily be fixed.
I also recommend you try Chrome and see whether that helps.
http://www.google.com/chrome is an alternative browser that may help.
What browser are you using?
If IE, then that is no longer supported. Use Firefox, Chrome, or Safari
www.apple.com/safariwww.mozilla.com (Firefox)
www.google.com/chrome