I had the exact same problem with my A10-5800k on an Asus f2a55-m motherboard. What I discovered is that with the ram in the first 2 available slots (which to Asus's credit and my ignorance were colored black, then blue to match the next 2 colorwise also) it would freeze every single time in roughly 5 min or so while gaming although would handle everyday windows stuff usually without problems. I changed the dimm in the second slot to the third and, VOILA! Not only did the freezes stop but also the video began giving me the performance I paid for (checked through windows experience it went from 4.4 up to 5.9).
Check your motherboard to make sure your memory is in the correct slots to be addressed correctly by the cpu.