Thanks for your suggestion acr, I know this document.
I still can't find any arguments for the fact that the trunk switch-config works with 2.5.3, but doesn't work with 3.0.1.
I think that I have exactly the same issue that you had. I have migrated one of our ESX from 2.5.4 to 3.0.1 and now the VMs have very estrange behavior.
I have one Vswitch with 2 nics teamed that are connected to a physical switch with the same trunk configuration on every port, but when I go to "Vswitch Properties"-> "Network Adapters", in the "Networks" column appears different IP ranges for every VLAN defined. And, what is worse, every time you go to this column the information is different !!.
I'm not a Network Admin so I don't understand quite well the physical switch configuration so, could you please explain me what were the steps you take to repair your physical switch?
Thanks in advance.
The way I solved it, was by untrunking the switch ports and adding the ports seperately to all the VLANs.
Now it works as it should.
By the way, I would not fix too much on what you see in the VI client, when you point your mouse to the Networks.
That is more an indication of some of the VLANs, not a detailed description of all of them. Something like: best effort.
Hope this all helps,