Problems with playing video or games

Hi,

I'm not sure where my problem is so I placed it in the Windows 8 topic.

A couple of days ago I suddenly had some problems with opening a video file in VLC. I heard sound but there was no image. I also have this problem in other media players like BS player or Windows media player. Also I'm not able to launch any game (FIFA14 or Starcraft 2). It just crashes and doesn't open the game.

I don't know if it's related in any kind but I'm also having trouble getting connected to my Wi-Fi network. It can't connect the first time I boot my laptop. I have to open the troubleshooting application that resets my network adapter before it is able to connect.

What I have tried so far:
- Reinstall VLC
- Changing video-settings in VLC. Windows GDI-output does work, also Direct2D-output works. But just having it set to automatic output mode won't work
- Reinstalled latest video drivers for my Nvidia Geforce GT650M and the integrated Intel HD 4000 graphics chip
- Virusscan with AVG and a scan with MBAM

So basically I've tried some things but I'm running out of ideas... Can somebody help me?

I'm running Windows 8.1 64-bits on my Asus N56vz-s4035

Thanks!