That will be because you moved the mouse or clicked again. Press continue and don't touch the computer, and the mod will load but it could take 10 minutes or more.
Try updating your video card drivers. You can download a newer driver from the Nvidia website. Or you can follow the instructions that ModMaker2009 posted above.
You just need to replace the prototype for the coroners van with the original one. Get someone to send you the original prototype and replace it, that could work.