Their response came back very quickly:
Response Via Email (Jonathan) 03/15/2013 10:31 PM
Thank you for contacting Ancestry.com in regard to the relationship calculator not working.
We are currently addressing the issue you are experiencing, and this will be corrected in the near future. Feedback from you, our valued customer, helps us correct errors and improve the website. Your patience and efforts to assist us in this matter are appreciated.
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If you need additional assistance, please feel free to reply to this message or contact us by phone at 1-800-ANCESTRY (1-800-262-3787) from 10am to 10pm EST, Monday through Sunday.
Customer Solutions Associate