I've built the pc myself, so the first thing my friends told me was that it might be because of DirectX not being properly installed or that I didn't connect hardware properly. But that doesn't seem to be the cause, because I'm not the only one experiencing these issues, according to other forum posts on various sites. (I'm still not sure about DirectX)
System specs:
CPU; AMD FX 8350, base clockspeed
GPU: AMD R9 280x 3G, amd catalyst driver beta 14.3 V1.0
RAM: 8GB Corsair Ballastix
SSD: Samsung 840 EVO 250GB
OS: Windows 8 64-bit, legal copy and updated
Mobo: ASUS Crosshair V Formula-Z
All hardware is running cool and not fully loaded or at top speed, according to software: GPU-Z, CPU-Z, Asus AI suite II and Msi Afterburner.