Issue resolved
The issue:
When I migrate server vnics to the 1000V and the ISCSI vmkernel is not pre-created on the VMware switch, it does not provide the proper mount to the ISCSI volume, even though the volume has been mounted to boot from and it looks like it's available to write to.
The fix:
Create the ISCSI vmkernel on the existing VMware switch before migrating the ISCSI port to the 1000V.
Thanks Marcelo