The bug

The "Graphics Device Unsupported" warning is displayed when the user attempts to change the graphics mode from "Fast" to "Fancy" instead of when the user attempts to change the graphics mode from "Fancy" to "Fabulous!". This means that if the user already has their graphics mode set to "Fancy", they will be able to change their graphics mode to "Fabulous!" without seeing a warning.

To reproduce

Please see this video: Warning shown at wrong time.mp4