I just created another manual invoice and the same happens. It's now having the right host name, but it's still adding the /client/ at the end which does not exist. 
  
Any more ideas? 
  
Hi Scott,  An invoice has been created for your account and is attached to this email in PDF format.  Invoice #: 942 
If you would like us to automatically charge your card, login to your account at http://my.hostingdifferent.com/client/ to set up auto debit.  Pay Now (No login required)  If you have any questions about your invoice, please let us know! 
Scott
hostingDifferent billing