If you have Google Apps and you just tried to upgrade your accounts but you got the error above.
- Remove the email associated to your domain from the google account via login at google accounts and going to my account and remove email@example.com
- Then point your browser to https://www.google.com/a/cpanel/yourdomain.com/GoogleAccountUpgrade
- Follow the instructions
- Log-out of your Google Apps product
- Log back in and follow the instructions
- Viola! You’re upgraded