Thank you for reaching out to us about this. I'm sorry to hear that you are experiencing this issue with saving. To help narrow down the cause issue I would advise trying an alternate browser to see if this will help. Sometimes an update or add on to a web browser will cause some conflict.
We would like to look into this further. Please send an email to social_support(at)constantcontact(dot)com with your username, a screenshot of this error message and what you have tried so far.
Thank you for your patience.