"Race Canceled" while trying to load a race

My AC Content Manager keeps crashing when loading a race.
I'm trying offline, and it works on a fresh install for a race or two before not working with any combination of car or map, modded or vanilla. None of the separate launchers work in settings and I can't seem to reverse it.

AC will launch just fine through the normal launcher via steam, and will even load with my modded cars.

Any ideas?


Belgium near Spa
As it seems to work for one or two races, I only see one possible reason for your problem ... an antivirus deleting or quarantining one or some Content Manager file.
It may happen any time with some antivirus suite .... I had this happening with Fanaleds one working for months and suddenly not working any longer.
Have a look in your security history ... you might find the reason there and even a needed CM file in its quarantine.

NB: even excluded from analysis, a single update may bring the problem again.