> gateway was duplicating(?) data out the PPP interface.  (Maybe it was
> sending something else---but it was sending _something_ out the modem in
> lockstep with the X protocol packets going to my X server.)

This smells like DNS or resolver configuration pointing your machine to
query an external server for reverse-lookups of new connections.

Have you checked for these types of problems yet?

Todd Whitesel
toddpw @ best.com