Safari 5.0.5 seems to not recognize the Flash Player plugin

Using Safari 5.0.5 in Mac OS X 10.6.7 on a 2010 iMac with a 3.0.6 GHz i3 processor and 4GB RAM I cannot view any content that requires the Flash Player browser plugin. I can view the content when using Firefox 4.0.1, Firefox 5.0.1, Chrome 13.0.782.215 and Opera 11.50, but when using Safari I always see a message instead communicating that I essentially need to install Flash Player in order to view the content. I have done so using the links on those websites as well as from Adobe's website itself with no success. I've used Adobe's uninstall tool several times, and even rebooted after uninstalling before reinstalling on one occasion. None of the solutions I've seen online have worked.