Rev C is a pretty junky router. If this was a recent install I'd ask for a Rev I which should be adequate for what you described. They tried to pawn off an older router on me when they did my install last Summer, after I objected they went out to the truck and came back with a Rev I.
If you can't get a Rev I out of FIOS, go buy a decent router or access point. You may want to do that anyway as at 40 feet I bet your speed is lower than you realize. A decent router equals more range and higher connect speeds.