Set Moodle to redirect to My Moodle - locked out of site!

I get the "coding error - must be fixed by a programmer" etc on just about every page.

If I try to get back to

admin/settings.php?section=navigation

in an attempt to reverse what I have done, I get the same error.

Where in the DB can I reverse this back to the default home page?

This is only happening to site admins. Normal users seem to be working properly. I hope someone can help me get this setting reversed please!