I usually play AWS in the auto-detected High quality setting but I tried using the Low setting yesterday for the first time in a long time. Every time I set quality to Low and click Apply I get the same error message below and when I click OK the game closes. If I restart the game right away I get the error again. The only way to prevent the error is to delete my Preferences.cache file and reset all of my game options and window positions and sizes. I customize almost everything so this has been a real pain. I tried again today after the C218 update and it's still happening.
I do not get this message with any other quality setting including Minimum, Medium, High, and Ultra.