Hmm, strange issue. I guess it's possible that the car's data in the GT Data file might have gotten corrupted somehow?
Something to try and narrow it down a little:
1. Create a secondary account and start GT5. It will automatically place the Edge Camaro in your new Garage.
2. Try and use it online and see if the issue still persists.
If it does, it's possible that you might have to delete your GT Data file and redownload the car to fix it.
However, a word of
CAUTION, deleting your GT Data file will cause you to lose all your saved replays, photographs, most or all of your garage car thumbnails, all GT5 updates, etc.
I only suggest this as a final possible solution to curing the problem, if it is indeed the downloaded car. Please search the forums for more information on deleting your GT Data file and the implications it presents, before deleting it. It can certainly cause issues for the unprepared.
Unless someone else knows how to delete DLC from their Garage without deleting the GT Data file, I'm not sure how else you would fix a possibly corrupted DLC file.
.
