Well, I thought Norton's fix had worked, but it's still not quite there yet.
I have a number of outlook.com email addresses that IDsafe holds the login ids and passwords for. If I select one of the others from Norton's "Multiple logins" bar (i.e. not the email address that comes up when I open the outlook.com login page), IDsafe appears to fill in the appropriate login id and password correctly. However, when I then click "Sign In" I get an error message in red - "That password is incorrect. Make sure you're using the password for your Microsoft account".
If I then click "Sign In" immediately a second time (without changing the login id or password that IDsafe has already filled in) then it works. So there is still a problem with signing into outlook.com after IDsafe fills in the login details.
This happens with IE11 on both my Windows 7 and Windows 8.1 computers.
Note that if I sign in to the email address that comes up when I first open the outlook.com login page, then it works ok.