We are running HQ version 2.0.0125.
Yes I am logged in as an administrator and in maintenance mode and part of a domain.
This is getting stranger. We are running an e-mail campaign (discount when customers give us their email) at our stores so we are capturing customer information including e-mail addresses like crazy. Two of my 15 stores suddenly had the email address field greyed out (but could enter everything else). We asked them to close the POS and reopen and sure enough everything is right again.
I applied the same logic to my issue at HQ, I closed HQ and reopened it and sure enough I can now edit the global customers' emails.
Lets hope it is one of those infrequent mysteries.
Reminds me of the old joke comparing Microsoft to a car that I won't repeat on this forum.
Thanks for your help