[imp] Double-frame browser issue

[Deja3 User]

Bring up the mail login screen  https://www.somewhere.blah/ 
Choose Dynamic Email (dimp)
You're logged in and everything is great.

Close the browser (do not log out of DIMP)
Open a new browser
Go to your webmail site:  https://www.somewhere.blah/
It brings up the login page, but now your URL is:  https://www.somewhere.blah/imp/login.php?url=%2Fdimp%2Findex.php%3Fnocache%3D10ycup3ghge8
If you login with that URL, you will have a leftmost frame of the IMP info, with another frame to the right of dimp, then the dimp inbox view to the right of that.

Anyway to prevent the IMP frame in this case?  There are two ways around this.

1)  After getting the URL with the stuff appended after the login.php, change the URL back to just https://www.somewhere.blah  and it doesn't redirect again.
2)  Login anyway, choose the logout button, then login again.

Why does Horde/imp/dimp redirect like that?  I believe this is a session isssue as the session was still valid, but with a new browser, it has lost the authentication piece.