RAM stability problem after months?

I have an Asus Maximus VII Formula mobo, 4790K, 4 X 4GB GSkill RAM rated at 2400MHz. My CPU is at stock clock, but Im using the xmp for my ram so it runs at 2400MHz. I've had it that way since I built the system. All the sudden a couple days ago I start having BSOD's and chrome says it ran out of memory or the webpage was terminated for some other reason. My mobo told me my overclock failed so I turned my ram down to 1600 and it seems to be stable. What could cause a stable overclock to fail after months? It was so bad the computer wasnt usable.

The extra speed and voltage, just like any overclock, may be causing the RAM to fail. You should try running some tests at a couple different overclocks with Memtest86, see if the overclock is the actual problem, or if it's just failing in general.

Another crucial component that can degrade naturally over time is your power supply, which is why it's recommended to swap them out ever few years or so.