Did "YouTube" put a (Block) on all Macintosh Computer users...so that only PC users can can see Videos now?

No, they are not blocked for a mac. You may want to check to see if you turned off something in your preferences panel for safari or whatever browser you are using. In Safari make sure that you have plug-ins enabled. Also, I believe that you need flash and you may want to make sure that it's up to date. What type of a Mac are you using and what browser version are you using (check "About ***" with *** being the browser.).