When I clicked on a lnk in an email from my revive ad server installation itself sending my my weekly report I experienced this message for the first time too.
I noticed it sent me to http:// version of the frontend login page of my revive ad server. rather than the https:// version I had been using hence no problems with this You need to enable cookies before you can use error.
I dont know how to fix the cause which would be for the report to redirect you to https:// version
so I just put the s in the url address bar and it went away and I logged in.
Some times what is obvious to you is not obvious to others. My questions may seem dim but your answers were very helpful and shone a lot of light on the subject for me. Thank you fornax!