how to reset the gnome keyring manager password

You could try deleting the keyring.

To do this look in the ~/.gnome2/keyrings directory, then delete the default.keyring file.

This won't disable the network manager prompt, but it will allow you to create a new key with a password you know. Despite the obvious security problem most people just use their log in password.

How to Reset/reinstall gnome desktop to Defaults

Just use that command downunder, and restart you comp or just move to text mode and back to grafical mode with,

ctrl+alt+f3 (move to text mode)
alt+f7 (go back to grafical mode), or just simply restart gnome or you comp.

rm -rf .gnome .gnome2 .gconf .gconfd .metacity