I too just had an email that SpamCop spit back & said there was no source IP so it couldn't continue: http://www.spamcop.net/sc?id=z5163609103zd...ede547e869ebbdz
I think it's tripping over the IPv6 header. I know it skips the 172.x.x.x header (internal IP) and should also ignore the 10.x.x.x IP header as well.
The other Received headers seem fine.