I've had that happen repeatedly with Connor. It seems to be triggered by either having a Night Sight item on an elf, or from going to Fel and back to Tram. Once the UO day becomes night, the night sight goes wacky. If it's a Night Sight item all you have to do is unequip then re-equip the item and you'll return to normal. If it's a Fel thing, there doesn't seem to be anything other than restarting your computer to fix it. At least nothing else that I've found to work, unless you want to carry around a Night Sight ring or something to equip then remove. I haven't tried that but logic says it should probably work.