Seems like there can be issues with running routing and remote access service can cause repeated packets
and make the network do funny things
It also looks like bridging to a wireless lan can be trouble as well.
thecodeblog spells it out here:
http://www.codeblog.co.uk/2009/06/22/web-platforms/vmware-duplicate-ping-responses/
Don't know if I like the VMWare "virtual switch" that they use for bridged networking in guest vm's
You might check on my other what the on the subject here:
blog/01259788481