Do you own (i.e. have you purchased from the steam store) the BMW and CORVETTE GTE's? I looks a bit like you may have downloaded a skin pack or mmod for these cars but don't have the actual cars the skins need to be applied to. Or I could be completely wrong.
@bgil66 this message appears cause you have installed a mod or skin pack that is not compatible with the cars
find it and uninstall it and the message will no longer appear