I think I've got the solution, go to youtube.com/html5 and then in the bottom of the page you have an option to disable the html test, that worked for me
Here's a risky thing u can try (It will delete all your settings and stuff). Click "Go" on finder menu while holding "option/alt" button --> library --> preferences --> delete "com.apple.Safari.plist" make sure ur safari is closed (quit safari completely) before u do this. hopefully everything will work fine. I was really frustated the last few days and did everything i could to try fixing it. i actually started using chrome instead until i came across that 32 bit thingy. i did that after i first reset safari and then delete the plist file.