I couldn't race some championships (GT300 being one of them, and therefore GT500 as you have to complete the first to unlock the other) as the game would crash once past the initial loading screen but onto the pre-race screen. The game would attempt to load the cars but it wasn't having any of it.
Since then, I can access every event and each loads absolutely perfectly.
Re-installing doesn't take as long as you think really, well, it depends on your internet speeds of course. I think it probably took 30 minutes or so before I could play the game again. Reloading the thumbnails was a bit tedious as that took some time, and the increased loading times at first were a little frustrating, but nowhere near as much as not being able to play the game properly!