I'll screenshot it the next time it happens, but yeah the task manager shows the memory usage inflating to 10-12gb instead of the normal 1-1.25gb. I don't get an error message or crash, just the game slowing down to the point where I'm unable to do anything. This seems to match up with other folks saying that the game's frame rate drops to almost nothing. It goes away if you close the game & reopen it. You don't necessarily have to be actively playing for it to happen - just have the game logged in for extended periods of time (like while I'm at work).