Up until yesterday the oil gauge in my 2001 Dodge Ram 1500 would go to 0 - the check gauges lite would come on and pressure would be restored just as quickly as it had been lost. Yesterday, the truck won't start at all - all gauges seem to be OK except the oil gauge - nothing happens when I turn the key. Could this be the oil pump?

well yes and it could also be that you need to add oil. In other words this all can happen when you need to add oil. though it could be that the sending unit is going bad.

usually the sending unit goes 0 to maxed out when it goes out. more than likely the problem is your oil pump.

not necessarily, becuase my truck would do just what he was describing when it was low on oil

check your oil sending unit.

Have you done any work on it close to the dash? Mine did that when I replaced the dash.