I opened a ticket with VMware as well. Their response was that because we are using a distributed switch that we can move the DB, but we need to move the hosts back to standard switches first:
Question: We are using a distributed switch, will that cause any issues?
Answer: This is an extremely important step ,as is vCenter feature and the new vcenter that you are going to install would not have dvSwitch configuration at all . Hence when you connect to the old database which has the dvSwitch configuration ,the might be issues with regards to connection with the hosts. We have to migrate the hosts networking back to Standard Switch and then install the new vcenter ,creating the dvSwitch configuration and migrating accordingly."
So, VMware seems to indicate that the distributed switch might not work correctly by just moving the DB and installing 5.5 fresh. And it seems Alex_G60 above experienced something along those lines "the hosts can't synchronize their dvSwitches".
Not sure where that leaves me. VMware is saying it can't be done w/o moving to standard switches first and I am leery to try it without their blessing. If I have to move the hosts back to standard switches, I don't see much reason to even move the DB. I only have one cluster and 11 hosts, so it wouldn't take much to just recreate and disconnect from the old vCenter and connect to the new once the hosts are on standard switches.
Thoughts?
Thanks,
Bob