Did you upgrade to Windows 8 from Windows 7.
I had done this and had some wierd issues after upgrading from the A8-5500 to the A10-5800K. But not related to my 7850 this issues occurred before I upgraded the PSU and added the card.
To correct these issues I did a Windows 8 Refresh, to do this you will need the disk.
Once I did this I have not had a problem with my HP box. The refresh will give you a list of programs you will need to re-install. I didn't install any of HP crap that the box came with.
You might want to do this, the refresh is pretty quick. Serveral other users have had issues and this fix them.
AMD A10-5800K, XFX 7850 Ultra OC Edition 975MHz 1gb, 16GB RAM, Win 8.1 Pro 64 bit, MSI 7778 motherboard, 500W PSU, HP P7-1235, CCC 13.9 WHQL