If you haven't signed the Terms of Service, you might see an error when trying to connect to Picasa Web Albums with the Mac uploader. You may be able to resolve this issue by visiting http://picasaweb.google.com and agreeing to the Terms of Service. After doing so, try signing in again. If the issue hasn't been resolved, please follow the steps below. Please note that these steps may be different on a browser other than Safari:
- Open Safari.
- Choose Safari > Preferences.
- Click the Security icon at the top of the Preferences panel.
- If 'Accept Cookies' is set to 'Never,' change it to any other setting. You should now be able to sign in to Picasa Web Albums via the export command in iPhoto.