Mambo - Tinymce - editing problems

I've been on the phone with a friend who is trying to edit a website I set up years ago using the Mambo platform. He would log onto the site and go to the editor, but when he tried to insert an image he'd get an "object not found error." He was using Chrome so I thought there was some kind of issue there. He doesn't have Firefox installed, so I sent him to Internet Explorer. On IE he had even worse luck - just a blank page. I went through all my browsers and was able to log in and edit with all of them. I did a Google search and found a hint that reminded me that I had to solve a similar problem a few years ago. Are you ready for the solution? He was going to "domainname.com" instead of "www.domainname.com." That was it! Even though Chrome would let him into the editor, it choked when it tried to open up the image insert popup. IE wouldn't even let him get that far. Adding the "www" fixed it in both browsers! That's one of those two hour problems that must drive phone techs crazy!