I apologize you are receiving this message when you are working in your account! Have you tried a different browser or a private/incognito window? Also, would you be able to get a screenshot of this message you are seeing? You can email us at social_support(at)constantcontact(dot)com with this screenshot, your username, the steps you are taking before the message appears, the name of the campaign you are working on, and a reference to this post. Having these details can help us to troubleshoot further for you.
I'm sorry to hear that you are having issues working on your campaigns! Have you tried switching browsers or using private browsing or incognito mode in your browser? It could be an extension or plugin within the browser that is giving you difficulties and these are not typically used when accessing our site using a private or incognito window. If this does not resolve your issue, please let us know!