Windows 7 - Problem With Playing Videos on VLC, YouTube, etc.

I think this is a bit of an unusual problem, but basically sometimes when I load my computer it will not play videos or load skype. Internet browsing and other applications seem to work fine but VLC, windows media player, youtube and skype will not run at all.

In saying this, I mean that I will try to play a video for instance and it simply won't play. No audio, no video, no error message.

Now what I have learnt though, is I can restart my computer which tends to fix it. This doesn't happen all the time, but roughly 1 in every 3 or 4 times I boot up my computer, I have this issue.

So yeah, it's somewhat annoying and I'd like to understand why this is happening and what I can do to stop it from happening.

Other notables are that my windows updates are up to date and as far as I'm aware, my driver updates are current also.

Did a sfc /scannow which found no violations and my computer specs are as follows:
Intel Core i5 2500K Processor LGA1155 3.3GHz CPU
ASRock Z68 Extreme3 Gen3 MB, LGA1155 Intel Z68
G Skill 16G(4x4G) DDR3 1600Mhz PC12800 RL 9-9-9-24(CL9Q-16GBRL)
Seagate 1TB SV35 7200.5 SATA 32MB
Asus ATI EAH6850 Direct Cu V2 PCI-E 2.1 1GB GDDR5 DVI HDMI D-Sub DP
DX11 Fan
Asus DRW-24B3LT 24x DVDRW SATA LightScribe
Antec Dark Fleet DF-30 Gaming Case
Corsair TX-650 650W ATX Power
Microsoft Windows 7 Home Premium 64bit OEM

Thanks