There were other reports about this problem, as old as 4 years, and I was hit by it too now. I have a Win7 x64 box running VMware Workstation 8.0.4 as host and a Ubuntu 12.04 as guest and another Win XP as guest. The same problem happens with VMware Player 4.0.4 too though. Both guests are bridged, but not both running at the same time. All mac addresses are different everywhere: router, host, guests.
Pinging any IP or host from the Ubuntu box, local or not (e.g. even google.com) results in seeing DUP! dupliact eping replies. Pinging the Ubuntu box from the, e.g. router or any other Linux box on the same LAN segment also results in DUP! duplicate ping replies.
Trying to innitiate PPTP connection from thr WinXP box to some host on the internet hangs at the verify user & password stage.
ssh'ing into any of the guest OSs is slow.
The culprit in my case: The RRAS service in relation with VMware on my Win 7 x64 host machine! Stopping it makes all problems go away. In my case it was activated because I accept incoming PPTP connections.
Googling around I found other reports that RRAS conflicts with VMware, e.g. http://www.codeblog.co.uk/2009/06/22/fixes-and-tweaks/vmware-duplicate-ping-responses
Can VMware please try and fix this? It's such an old problem. I need RRAS so disabling it is a no-no for me.
Regards.