For any of you thinking about building a new vCenter on a 64 bit OS so you can upgrade to 4.1, you should just export your database and import it on another machines. This is especially true if you use vDS's (vNetwork Distributed Switch), remember that these are stored on the vCenter and will continue to work on the ESX hosts, but will be difficult to modify/import/recreate on your new vCenter 4.1 server. To compound this difficult situation, if you are using iSCSI to reach your shared storage you will be in more deep stuff.
If you find yourself in this scenario, and you know what you named your previous vDS's, PortGroups, etc.. you may be able to recreate it without much difficulty. It gets more difficult when your using 8+ nic's per ESX Host. If you just need to start from scratch, it'll take a reboot or two of your ESX hosts (especially if you use EVC CPU masking) to get everything ripped out so you can start over again.