I am getting this exact error. I am trying to update the email address on the confirm.php page the checkout wizard created. For some reason under Server Behaviors it shows as Universal Email 1 (Mail for Linux). Not sure why since I am not using 1. This is my setup:
Windows 7 OS, Dreamweaver CS5.5, eCart5.0, UE 2.8.
I first received the error when I double clicked the Universal Email server behavior. Then I followed instructions to clear the cache. After clearing cache I was able to get to the area to make changes to my email settings. However, as soon as I click the OK button I receive the same message. At this point I cannot access UE without clearning the cache again. So basically I can clear the cache to access the area to make the Email changes but I receive it again as soon as I try to save the changes. Then I have to start all over with clearing the cache. No changes are ever made.
I have removed extentions and reinstalled them. Done everyting the forums suggest to do. Any solution to this?