The setup up has one vSwitch with two VMKernel ports on it. One for ISCSI and one for NFS traffic. Each VMkernel port group is on a different IP address and VLAN. I can provision ISCSI datastores without issue, however when trying to provision NFS datastores, they fail because VSC is trying to mount the volume using the ISCSI IP address/interface.
If I remove the ISCSI interface from the provisioning setup in the VSC settings, I can successfully provision an NFS datastore without issue. In the VSC.xml file the IP address for the NFS interface is listed above the IP for the ISCSI interface if that makes any difference.
It appears you are hitting a bug fixed with the VSC 4.0 release which is already GA. I believe the way it works now with VSC 4.0 is that you can restrict use of certain IP/Networks for mounting NFS or iSCSI datastores.