this sounds more like issues with codecs, or rather some mess in your system and some apps fighting for video files
personally i just use
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codec [ full ] and
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codec, thats all, no problems with any games or videos or watching online
about unity and some other issues that people are reporting - in my ocasion i have found issue with unity and citrix receiver simple dont like each other, i have followed this guide -
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- almost on bottom of page, and that helped with issues with citrix and unity
on some other ocasion i have issue that my instance of unity webplayer was causing issues, updating it resolved other issues
hope this tricks helps anyone