Moutain Lion browser issues

Hey guys and gals :-),

After upgrading my new MacBook Air to Mountain Lion I started noticing strange issues while browsing, some sites aren't working properly for some reason.

Some examples:

- Mouse-over anga titles to get more info on them over at mangafox.com doesn't work

- The live stream (flash) of the olympics isn't loading at all at http://nos.nl/os2012/ (Dutch news site, streaming only works if you live in Holland :-()

I can't pinpoint the exact problem because these issues just seem to happen on random elements for some reason, I can't find any related cases online either (tried searches on "Mountain Lion Browsing problems" etc. but nothing came up). The problems occur in all browsers (opera, chrome, firefox and safari)

Have you ever heard about this or experienced similar issues ? I would love some help here, this is getting really frustrating :-(.