1998 Dodge Ram power steering quit suddenly?

We parked the truck 3-4 days ago due to a loss of brake pressure. We'd dealt with that problem before, and know how to fix that issue, so that's not my problem. My problem is this: when we went for a test drive after fixing the brakes, we had no power steering! It worked fine before we parked it, and now it's gone. Some investigation revealed that the fluid was low. Filled it, and it still didn't work. More investigation showed no obvious leaks underneath, almost non-existent pressure in the power steering system, and a funny smell to the fluid. Not really a 'burnt' smell, but it doesn't smell right either. Is this likely to be a failed power steering pump, or something else? It seems a bit odd for the pump to fail while not being used. Any input would be great, thanks.