Existing LUNs appear with old names on new servers

Hi,

I have an existing SAN with some ESX 3.0.2 hosts attached.  Many of the LUN names were changed some time ago.

Recently, upon adding four new ESX 3.5 hosts to that storage group in the SAN, and re-scanning HBA, the LUNs appear, and are accessible, but with their OLD names!

Why is this?  And, equally important, how can I rename them so they'll appear consistently across hosts?

Thanks!