Ok - I raised this as a ticket with support a week ago and I've heard nothing...
It's fairly simple.
I've had a zumo for 4 years so I signed up for a my garmin account with this username =^..^=. No problems - I can sign in to mygarmin..
I've registered my city navigator with this account name. I've bought new computers so I need to transfer my maps over. No problems - I can do that in the mapping application.
I can (obviously) sign into this forum using this account name.
I can sign into the droid app using this account name
But I can't sign in online to Garmin connect because apparently "You have an invalid character in your username".
Perhaps the message should read "Garmin apologises for not having consistent sign in validation across it's interfaces"