David Alcock backs out of a problem:
This error isn’t to do with my login as such, it’s still there with sysadmin role membership so I don’t have to do anything too drastic like restarting SQL Server with the -m or -f startup parameters and recreate it. The error message is telling me that my logins default database cannot be opened, which is more than likely because I’ve deleted it.
Click through to see how David got out of this issue. This is a big part of why I highly prefer not to change the default database from master for logins..