A few different times the Time Capsule has started flaking out: the light in the front starts flashing orange, and even though Macs seem to be connecting to it, they can't get outside connections. I suspect this may happen when there's a guest using a PC laptop, but am not positive.
after this I manually set the channel to 8 (it was using 11 a little while ago, and a number of other networks were too). We'll see if that helps.
Nov18 update: the problem seems less frequent, but hasn't gone away completely.
A couple possibilities
Cable Modem service might be flaking out
maybe some non-current Lap Top, like my old IBook which The Boys use occasionally, or the babysitter's Think Pad, might be causing problems, like Dave Winer's Net Book issues. [z2008-10-17-Eeepc Under300]
Nov20: now I'm thinking it's less about hardware clients, but rather associated with The Boys playing games (World Of Warcraft and browser-based games).