VAAI - ESXi 5 - status "unknown"

I am currently having an issue with VAAI showing status "unknown" for our EMC SAN connected LUNs.

We do not see this issue with ESXi 4.1 using the same EMC SAN.

We are using FLARE 04.30.000.5.517 - which is the latest release from EMC.

We are using the same configuration on the SAN for ESXi 4.1 and 5.0.

Rescanning and rebooting has not solved the problem.

I have also done VM copy's on the disks and the status has NOT changed.

Is anyone else having this issue?

Is anyone else successfully using VAAI with EMC CX4-120 and ESXi 5.0 ?