Ah, finally, I have figured it out! Sorry for starting a new thread, but I think you should add AMD's new APU's to the troubleshooting guide. The problem was, that I installed the CPU+GPU+MBO drivers from my MBO vendor, ASUS. What I didn't notice was, that the GPU drivers in that package weren't a full version, just a part. So I went to the official AMD site and downloaded the CCC from the following link:
http://support.amd.com/us/gpudownload/wi...n8-64.aspx
I hope this will help other people, too.