I'm having this strange issue on a clean install of ESXi 5.0 and adding it to vCenter. It times out with the error timed vpxa out. The vpxa logs on the server contain no information as well. I did some digging and tried blowing away the vpxa config and restarting the services with no luck. I restored the config file and added a <hostIp> since that was missing and that did nothing as well.
There is not a firewall between the ESX and vCenter server.
Has anyone seen this before?
Welcome to the community.
Try downloading the fresh copy of ESXi5 ISO Image from the VMware website and install on host. Then add to vcenter should resolve the issue.