Okay, here is not a solution for everyone, but a little guide for those who have a disc copy of the game:
If you have already installed Patch 1.3.7 you have to uninstall the game. Don't worry, your save status will be preserved. Now you put your console offline and then reinstall the game. Go into the game and ride on a long straight for 5 seconds in the slipstream of an opponent. After you have done that, you can go online again and install the patch or do the "variety is spice of life" achievement too. This must also be done for some without the patch (see guide in the achievement). I wish you success!