The routing table with in ESXi takes precedence over what ever you configured within your portgroups.
This was not an issue in ESX as the Service Console and vmkernel had their own seperate routing table to deal with..
And I do not believe ICMP will reveal such an issue.... So ping'in may seem fine..
Try to configure your vMotion vmk interface with a different subnet, and Im sure its all good...
/Rubeck