Hmm, did you try setting the router to be the same IP/subnet/gateway as the laptop you know works (not connected at the same time, obviously) and attempt to ping it from somewhere else? (In other words, can the Charlie switch even figure out that a router is connected in the first place?) Of course that assumes you don't kill pings at a firewall somewhere..

And now that I think about it, swap out Charile's switch for a bit and plug in one of your "other switches" that you aren't sure are working, and then test a laptop through that - maybe something's just specially set up in Charile's switch (If this paragain is indeed the issue, I have no idea since I'm not familiar with them - but it's worth a shot). If it works perfectly, reverse the current way - plug Charlie's switch into the "other switch" and see what happens there - if the Charlie network runs smoothly and the "other switch" works fine, then everything is okay..