Netscape Login Loop ?

Hi! I just installed this marvelous forum last night... it is beautiful! As a newbie, I have but one problem. The forum runs excellently on IE6, but when I go to Netscape 7, the following happens:
A member can login successfully. The page reading "Successful Login" does appear. However, when it automatically (or through manual click on link) returns to the Main Forum, it somehow loops out of the login, and there is no recognition of the login. (That is, there is no icon with the words "logout - name", nor any features working other than to view the forum as a guest might.)

And, a new user registration is acknowledged in Netscape, but again, cannot login. (The user can then go to IE and use the entire forum, so access to the database is not the problem).

Any words of wisdom for me? Thank you very much!