When I login to opendns I cannot login with the same username and password into dnsomatc. So I do a password reset in DNSomatc, then I can login, but I can then no longer login to Opendns and vice versa.
You should open a support ticket with OpenDNS. I have no problem using the same credentials for OpenDNS and DNS-O-Matic (in fact I don't think the two would work together properly if you weren't using the same credentials) and haven't heard of anyone else having that problem.
