Hi eanajat!
In my case, all cars are gone, I can't drive any of the 5. Here's a screenshot of the EasyDrive menu, there should be another Bugatti there, but it isn't:
https://dl.dropbox.com/u/49474825/no_Bugatti_.png
In my Origin account, if I click "game details", I see that the Ultimate Speed Pack shows up as "installed". I can't access my order history at the time, the the Origin website is really, really slow. I will keep trying. I have the e-mail they sent me after buying the DLC, though, so that's also proof.
Here are more screenshots that prove I bought the Ultimate Speed Pack and drove these cars.
Origin in-game store (it's in Portuguse, but you can see I bought the DLC): https://dl.dropbox.com/u/49474825/DLC_bought.png
What happens if I try to switch to a DLC car: https://dl.dropbox.com/u/49474825/Go_to_store.png
Hennessey Venom GT Most Wanetd beaten: https://dl.dropbox.com/u/49474825/Hennessey_beaten.png
Multiplayer progress to unlock the new cars: https://dl.dropbox.com/u/49474825/MP_progress.png
Singleplayer progress: https://dl.dropbox.com/u/49474825/SP_progress.png
Singleplayer progress 2: https://dl.dropbox.com/u/49474825/SP_progress_2.png
Any help would be appreciated. I will also try to unninstall and install the game and the DLCagain.