I have a 2004 Safari Zanzibar (Class A) Monaco mfg. I turned on all the 12 volt interior lights and after 20-30 minutes the overhead florescent lights and the passenger side lights suddenly went out....
It sounds like your salesman's switch is turned off, or the relay it controls failed (they do that a lot) Assuming of course that your safari is a Monaco under the skin.
I have a "salesman's switch" on the panel right inside the door, the front of the passenger armrest. It control's a big relay in the front run bay (drivers side front basement compartment) and it turns off most of the 12 volts, lighting and all that, but does not shut off the fridge and heat and such.