I have the same issue. I am working on windows 7.
on my laptop and another pc (both windows 7 64 bits) we have duplicate packets. (4 packet is sent instead of every packet and on each duplicate I can see the ttl that is decreased by one ).
but on some other laptops and pcs, (all windows 7 but not sure which one is 64 bit) there is no problem.
I have vmware installed.
bests and looking forward for you reply.