If you downloaded and installed the 70's GT carpack before 6:30 pm January 21...there was an error in the download.
The folder named Chevrolet Corvette was misspelled and needs to be deleted.
You may take the Corvette car folders out of the misspelled folder and place them in the original Chevrolet Corvette folder (the one that came w/ the game) or just delete the misspelled folder w/ its contents,re download the 70's carpack and let it correct itself.
I am very sorry for the inconvenience.
If you need any help just post here and we will do all that we can.
Thanks,Bob Dunlop