"401 Authorization Required" message makes scores invalid

Frequently when saving a score I have been shown the message "401 Authorization Required". After I get this message and go back to the home page, the score I've been working on will be "invalid" and I won't be able to open it. This is incredibly annoying as it has happened to scores I've spent weeks on and rendered them unopenable. How do I fix this, and can I get the "invalid" scores restored?