Started using Windows 8: Strange Flash Video Issues

My machine was upgraded to Windows 8 from Windows 7. It is Sony Vaio.
And I have so strange problems since first day. When using metro ui (or windows 8 ui) I could never play a video.

I really mean it. Directly, apps are closing themselves when I try to play a video. Also could not use camera app.

Then, I tried to update NVIDIA Driver. I had great hopes about things which should be fixed.
ZBAM!
Yeah, it really worked. I started to watch videos.

2 days later, problem showed itself again.
I updated driver again.
Fixed again.

2 days later, problem showed itself again
...
...

Then I thought waiting some more until 2 days ago. Then I updated it again. Fixed again but this time,
I really thought it is fixed. I tried to shut down my pc and started again. It was still working.
I restarted my pc. It was still working.

In the end today, I left pc alone to download some files. I went outside.
When I was back, my pc was plugged out from socket.

I restarted it, and this problem was still there. It makes me frustrated.