Video's don't play in any browser.

Okay so everything on my computer worked fine until Saturday and now I can't seem to stream video from most streaming sites on the internet, no matter what browser I try to use.

I'm running on Windows 7 Home Premium. 

I have the most Adobe 12 in here.  I have tried updating, then I uninstalled and reinstalled flash.  I checked my java, updated my video drivers and nothing seems to be working here, but confusion where flashplayer exists. 

When I try to play a video on youtube while using Firefox, I get just a black screen with no sound.  The same happens with Dailymotion.  But with vimeo, and facebook, they occasionally play.  With that said, they will play so long as I don't attempt to do any fast-forwarding or rewinding of the video, then it just stops. 

When I try to play a youtube video using Internet Explorer, it tells me that I need to update my flash, but then it will play the first 5-10 seconds of the video and completely stops even trying to load. 

I'm not sure what to do here, I assume it has something to do with adobe, because of the confusion in IE about whether or not I am updated to the most recent version.  I should also mention that for the hell of it I decided to try and update again and after twenty minutes of trying to get the file to download, now I'm getting an error message that says Certificate authentication failed.  Please reinstall to correct the problem.

Any help anyone could give me would be great.  I can't stream anything and I'm on a computer that is pretty quick and fairly new.

Thanks!!