You see this error message on a domain that has exceeded its assigned bandwidth limit.
To fix this problem follow these steps:

1. Login to the whm with your reseller username and password
2. Create a new package and assign more bandwidth to the new package. Make sure you enter a value for the bandwidth field and do not set unlimited option there.
3. Click on the "upgrade/downgrade an account" item on the left menu
4. Select the name of the domain with problem from the list and then click on modify
5. In the next page change the newly created package from the list and click on upgrade/downgrade button.

Your domain should now be on the new bandwidth limit.