I hit this problem when I was adding code to support storing encrypted passphrases in gnome-keyring for subversion. When we add a new key to the default keyring we are prompted for a password for locking/unlocking the default keyring. Sometimes I forget the password which I gave to this default keyring, which prevents me from viewing the default keyring and the keys associated with them, using the gnome-keyring-manager.

I found out that these encrypted passwords all those associated information about the keyrings are stored in the file '~/.gnome2/keyrings/default.keyring' in Debian based distros. Just deleting/removing this file will free all the keys and deletes the default keyring of your gnome keyring.