Strange iSCSI port binding issue

I'm having a very strange problem with my iSCSI SAN that I can't work out.

Previously, I was running ESX 4.0 with multipath iSCSI working just fine. I did an upgrade to ESX 5.1U1 and now I can't get iSCSI multipath to work.

Here's the thing though, when I have no vmknics bound to the swiscsi adapter, I can see my storage just fine and can read/write as I should. As soon as I add the vmknics to the swiscsi adapter and reset the iSCSI session, I can no longer see my storage.

This is the current state with no vmknics bound to the iSCSI vmhba and the storage working fine.

My vmk ports are as follows:

vmk0 - Management interface on 192.168.113.x network on VLAN 113

vmk1 - iSCSI 1 on 192.168.116.x network

vmk2 - iSCSI 2 on 192.168.116.x network

vmk3 - Isolated network for vMotion on 192.168.115.x network on VLAN 115

The output of esxcfg-route -l:

192.168.116.0     255.255.255.224       Local Subnet     vmk1

192.168.113.0     255.255.255.0          Local Subnet     vmk0

192.168.115.0     255.255.255.0          Local Subnet     vmk3

default               0.0.0.0                    192.168.116.30     vmk1

If I ping my storage using (vmkping -I vmk1 or vmk2) I get the correct response.

My virtual network is as follows:

And the adapters are bound as follows:

So, right now with NO vmknics bound to my iSCSI adapter, I can see and browse my storage just fine. But, as soon as I add one of the above vmknics to the Networking Configuration tab of the adapter, I can no longer see my storage.

Any ideas? It's causing me to lose lots of hair.