Did you try a BIOS roll back to the previous version to see if the issue mentioned above are BIOS related?
What is the part number and manufacturer of the memory sticks that you are using?
All four sticks are Corsair Vengeance 8GB) DDR3 1600 MHz (PC3 12800) Desktop Memory (CMZ16GX3M2A1600C10).
I've been hesitant to make any more changes to the BIOS. Is it safe to rollback after updating? How far should I rollback to?
You should just try to roll back to the version that you were using before as it was working fine in your system. it is safe to do that roll back.
If you do not know what version was installed, try using the previous version on the web site. For this, use the BIOS recovery method as shown here:
The file you need to use is posted here: