Memory leak. Running Afterburner or just using task manager, the game starts at 3gb ram usage, then SNAP, it goes up and up and up until it's about 14gb by the time you load a save and then sits at your max (mine is 16gb). After that, whenever it tries to bump past your max RAM, it'll freeze up. Someone else chime in once you have a chance to verify this so we can have UBI find and fix the leak asap.

And yes, when I close GRW my ram goes back to normal, I booted rocket league to make sure it wasn't my system and the ram usage holds strong at 4gb. It's 100% GRW.

My specs:
i5 3570k
980ti
240gb Intel SSD
16GB RAM