First, you should really check that AD box again. Like pmj says, you need that and ideally would use the pass through authentication. Failing pass through, I've got a partial solution to your pop-up authentication box issue.
Digging through the login.aspx file, it seems that if the URL string includes a get variable of "Authentication" which is set to true, you don't see the authentication box. I just tested on my SD box and found that
http://YourHost/ProcessManager/login.aspx?Authenticated=true
put my straight to the login page without the pop-up box. To make it a full solution, you'd probably want to use some sort of URL rewrite code to direct users to that URL automatically, though you could also probably modify the javascript in the login.aspx file to accomplish the same thing.
EDIT:
Yes, I was able to change the login.aspx file to skip the authentication box. In the function "CanAuthenticate", change:
catch (e) {
ShowLoginControls();
}
To:
catch (e) {
window.location = window.location + '?Authenticated=true';
setTimeout)ShowLoginControls, 3000);
}
Now, as usual, there may be some very good reasons to not do this, so use at your own risk. I'm sure Symantec would not support it and it would likely be destroyed on upgrade or reinstall.
EDIT 2:
Upon further testing, the above didn't work. Using a much-too-large hammer, I decided to comment out everything in the "CanAuthenticate" function and simply put in one line of:
ShowLoginControls();