Open up Applications->Accessories->Passwords and Encryption Keys
Right click Passwords:login and unlock it.
You should be able to expand the tree and find a listing for vino. Right click and delete it.
Close Passwords and Encryption Keys.
Open gconf-editor as and navigate to /desktop/gnome/remote_access
Enter in your BASE64 encoded password into the vnc_password key.
Save the config and close the editor.
Reboot and you can now use your VNC client to connect to your machine without being first prompted with the keyring.