I am more than tempted - I actually did so, and was surprised by the results. My power brick for the Dell says 65W on the bottom. I measured the current draw under various scenarios, and here's the power draw from the AC side:

battery removed, dim screen: 55W
battery removed, bright screen: 60W
battery charging: 100W

So, having a battery in place (that's not fully charged) substantially raises the current draw, and pushes it well over the 75W maximum of the NWA 120VAC outlet. Based on these results, removing the battery will solve the problem.

It's still interesting that having the battery in place and charging works on CO's 75W emPower outlet, and even though that's a DC outlet, I highly doubt that the AC->DC conversion is wasting 33% of the power. CO's outlets must actually provide more than 75W before cutting out.

In any event, problem solved.