I'm currently racing LFS with a laptop connected to a monitor. Sadly the monitor cable is quiet old now and with the movement of the mounted wheel and the shocks and vibrations caused by it, the cable got unpluged at the monitor end. When I fixed that, looking at the monitor I saw my virtual gauges turned to black (R 0% G 0% B 0%, needle and background), while my standard settings are R 100% G 0% B 0% for the "clock needle colour" and R 100% G 100% B 100% "clock background colour".

Yesterday this happend for the second time.

It is probably just a reset error of the settings or you may have pressed a shorcut that changes between the guages setting such as virtual guages and all guages.However iv had a similar setting with my wheel settings reseting after i closed the game and i would just save the .cfg file befor quiting the game =)