IE11 not writing cookies

Hi, I discovered a problem writing cookies in IE using a basic document.cookie script. It's working in Chrome, FF, and Safari. I've tried other coding forums, but haven't had any responses.

I checked the IE security settings and have Protected mode off and changed Security to accept cookies from all sites. Restarted IE after the changes, and still I can't get document cookie to write with this test script.

function isCookie() {

    document.cookie = "testcookie=test";
    var cookieEnabled = (document.cookie.indexOf("testcookie") != -1) ? true 
      : false;
    alert(cookieEnabled); //alert true
    alert(document.cookie.indexOf("testcookie"));  //alert 0
    alert(document.cookie); //alert testcookie
    return (cookieEnabled);
}
isCookie();

I have a Mac and used IE11 via VirtualBox to test, as well as a separate Windows 7 laptop. In both cases, the alert messages above are 'false' and '-1' only in IE. Another IE user is encountering the same problem.

We are using cookies to manage Remember Me and Terms of Use settings, but I can't implement it until I get past this one and so far, haven't had any luck in research.

Ideas most welcome!