So I guess my old RAM was total rubish... I removed the old 4GB, so now I "only" have 8GB and I was able to OC back to 4GHz without a problem. Was even able to lower the voltage from my previous (OC Voltage) 1.251 to 1.232. I will need to run some Prime95 and after that I will try Windwaker again and post an update.
Edit: Ok, it's working like a charm Got it at 4 x Native resolution, 2 x Anti-Aliasing and 16xAnistrophic Filtering
Edit: Ok, it's working like a charm Got it at 4 x Native resolution, 2 x Anti-Aliasing and 16xAnistrophic Filtering