The screen capture tells it all. What is a good subdivision cache value to eliminate this.
Try reducing the number of threads running.
What size did you use in this render? It seems like this is a commonly misunderstood value. Best thing to do in most cases is use 100MB *per render thread*. If you're using 8 threads, use 800MB. You can go as low as 50MB/thread (400MB for 8 threads), but you risk lowering rendering speed a bit. Above all don't just crank up the render cache setting because you have "tons of memory" and figure "why not use it all to make it faster?". A scene like you appear to be rendering should not be giving you memory errors (unless your detail settings are insane).