Lights Turn Off When Single Buffering?

I know this is rather an obscure question,
but I thought I’d throw it out there anyway
hoping that someone else had encountered and
solved this problem. I’m working on an SGI
Solid Impact workstation. It cannot do true
color and double buffering at the same time.
When I want to capture true color images I
switch my applications to single buffer
mode. Sometimes when I do this (not always)
the lights in my scenes turn off!?! Why?
How do I turn them back on? I’m making some
animations for a deadline next week and
really don’t want to do them dithered! They
look awful that way! Thanks. mfw.