Okay, so looks like I've completely broken AC. The only thing that changed was I installed a free trial of another game, and verified the integrity of the AC game files to see if there was a way to prevent Steam from automatically closing when I started a race, as that was the cause of an issue I mentioned on here yesterday. It re-installed some 1800 files, maybe that's the issue here, but I am far from an expert in these sorts of things. For whatever reason, after that finished and I shut my PC down, it logged me out of my steam account, so I logged back in, and opened CM. This brought up that 'first start' screen where you've got your steam name and some optional extensions to install, and not a single thing has worked since then. All the Kunos cars had reverted back to their base preview pics and brands, and when I tried to race any Kunos car it would cancel the race and tell me that their data was heavily damaged, even though it clearly isn't, I've checked the unpacked data. Mod cars simply brought up the 'race cancelled' notification, and nothing else.
So I uninstalled the game, and then reinstalled it overnight, this has solved the past few issues I've had with it, but not this time. If anything, It's made things worse, as now every car just brings up the 'race cancelled' notification, giving me absolutely no idea as to what has occurred. The tracks seem to be fine, those get loaded no problem, but there are certainly issues with the cars.
So please, if anyone has encountered a similar issue and knows of a potential fix, help me out here, I would be so, so grateful!
Enjoy your weekend,
RenaultDJRTP