We're currently investigating some reports of in game stuttering when ranking up during a race or while in the garage. If you're experiencing either or both of these issues please respond here with a DXDiag so we can expedite this investigation.
Instructions for gathering a DXDiag can be found in the help article here: http://bit.ly/GatherSystemInfo
For me it can happen randomly, and from time to time the issue can be almost non existent, while other times it's so frequent that I need to close the game and reload it. Only a couple of times has my game actually crashed during one of these stuttering episodes in the last few of days. Which I guess is a good silver line to it.
But yea like I said it can happen randomly for me, doesn't matter what I'm doing. However it's by far the most prone to happen when I'm in the garage, in the menus, or driving near an event/garage/dealership (any place on the map that may load a race or a new scene).