I had some weird problem with the Xbox 360 multiplayer last night.
I'm far into rank 26 and I finish a race. I rank up to level 27 and it shows me what I unlocked. It then says, "multiplayer error when loading profile", or something really similar to that. It kicks me out of multiplayer and so I log back on to find that while the stats of my race remain (how many top 3, firsts, etc), it didn't rank me up and I'm back at level 26.
It did this 3 times in a row before I said screw it and stopped playing last night. I hope this isn't some bug that prevents me from ranking up, but instead just some problem I was having last night. Regardless, the game is awesome. Perfectly done!!