Can not ping or connect from second ESXi host

[KernalDebugger]

I have 1 ESXi 4.1 host successfully connected to my ReadyNAS 3100, using it's own VLAN, jumbo frames etc and it's running very well. All pings and vmkpings work.

When I try to connect or even ping from my second ESXi 4.1 host to the ReadyNAS I can't get a response (NICS are teamed on the NAS).

I can ping the first hosts NAS vSwitch from the second host and I can even ping a PC also on the NAS VLAN in both directions from the second host so I know the network is fine. I can also manage the NAS and ping from this PC.

Any ideas appreciated.

[KernalDebugger]

Useful info for others:

It seems that although root directory access wasn't necessary when the NAS was part of the domain, removing it onto it's own VLAN in a different IP range wasn't great for one of the ESX hosts. On this host after the VLAN move I had to recreate the vSwitch to enable jumbo frames (with the same IP address) and it seems this was when the connection to the NAS was lost.

So I added both hosts IP addresses to the root access list, took the opportunity to upgrade to the latest firmware and now it's fine.