For some reason the Linksys hub wouldn't always do PPPoE correctly -- it wouldn't be able to log on, for whatever reason. I'd get around that by hooking the modem directly into my computer via built-in ethernet port, logging in, then hooking it up to the Linksys hub and trying again -- for some reason that worked ok.
I updated the firmware hoping it would work. Now it doesn't work at all. I mean, the wireless part works just fine -- computer can connect to hub just ducky. Hub cannot, alas, log on to net via DSL via PPPoE, at all, not one bit. Grrr.