I can answer most of your questions...I have been playing GT2 since it's release on Christmas eve in the US
after approximatly 100 days, a game glitch remove's the car's data in those particular slots, and replaces it with the Track record data and user name...after this happens approximately five times, it cleans the garage out on you, except for the car your in.
remember GT2 was rushed to production, and mega botched.
also, there are THREE versions of GT2, PLUS the greatist hits version
put your disk in your comp...their should be a file folder labeled "FAULTY"
TO TELL THE DIFFERENCE WITHout the comp, check the Taurus SHO...only the 1.0 version of the game givves a race conversion...to a NASCAR body...this is copyrighted to hell, so they had to remove it.