can't edit existing subdomain
3.1 bug, domain control module is on (may or may not matter)
I have added a domain to a client, and the client can add a subdomain under Sites > Subdomain for a website, with no apparent problem. However when editing that subdomain after it's been created, the 'Host' shows the full fqdn with one letter missing at the end, and the Domain select list is empty, and you can no longer edit the subdomain, hitting save gives an error (Domain is empty).