Whenever you have black textures, it's always a missing texture. A missing texture in GSX can only be caused by not having installed a vehicle update which was released after the date of the installer you originally used to install GSX. Vehicle liveries are not automatically updated with the Live Update system, only the actual GSX code is, and I believe the manual says that.
Also, the full installer is always kept updated so, to be sure you have all the latest vehicles liveries, either download one of the vehicles updates, or simply download and install the latest full installer.