There is a known issue with AMD causing lockups: https://bugzilla.kernel.org/show_bug.cgi?id=196683
It sounds like you might have that if you get multiple freezes every day. I was also experiencing this problem after building a new AMD machine and that link helped me. To summarize the solution seems to be upgrading your BIOS. Some people don't have luck with that in which case there are also several workarounds given which reduce the problem. Incompatible ram could also cause such freezing. It might also help to check in dmesg for errors.
