why i cannot play and playback some videos on youtube at random time of the video?

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for example a 5 minute video... whenever i click the video on its time bar, the video starts to play again from beginning or 0.00 minute.
if i want to play the video from minute 3.00, its impossible for me now, it goes back to 0.00.
this happens to me from yesterday after a "500 error", but im not sure the problem is related to the error or not.
but some videos that i found to have the problem yesterday, didn't have the problem since today.

i'm using windows 8.

the same videos i tried on other pc windows 7, i have no problem as above.

i have tried both sign in and sign out youtube, mozila firefox, google chrome, reinstall windows.... the problem occurs in all situation and i didn't find solution.

is this a problem related to my windows 8 pc?
how to solve the problem

i need to know the cause and the solution for this problem, thank you.
for example this video https://www.youtube.com/watch?v=g2drZ3lysIE
but i can watch this video on this page without the problems above.