I got a bulb out warning on mine last weekend when I went out for dinner
with the wife. They were fine driving out there but after our meal the temperature
had gone down from about 4 degrees C to -2.5 degrees C and as soon as I started
the car I got the bulb warning, hopped out and checked and both were out.
Switched off ignition, back on again and they were fine again. Just a glitch I reckon.