A packet got corrupted between the source (207.226.80.1) and your masq
box. One or two are normal, line noise, dodgy network cards etc. If
you get a lot it could be a problem with your PPP link. Some users
have reported problems with PPP compression options (especially VJ
header compression) where there is a mismatch between Linux and your
provider's terminal server. Disabling compression often helps. You
could run pppstats and check the error count, too high a value
indicates a line or protocol problem.