Lets see...
1) Session object is of the browser window ok's.
2) In the above reply cookie is mentioned but i guess in your case it doesn't come in play because yor never mentioned it and hence i am making the guess you are not using it by urself(i.e. explicitly for storing the state).
Since you are talking about sessions let us concentrate their it self:
1) Like i said before Session object is of the browser window of if you do ctrl+N or File-->New-->Window the same session object is used by both the windows so your condition bound to happen.
2) like is you are logged out of one window you will be logged out of the other one as well i.e if you are using the session object to check the state of the object.
3) And the form data will be replicated if that is in session.
4) If your not properly logging out of the other window (created as above) add some how log-in again the both the user will get changed or should i say the information in the session object will be replaced by the new information and both windows is now using the same new information.
5) Now if you open the new browser by clicking on new window than different session object is created you can check that by trying to retrive the logged in user information before putting the new one their.
Please reply back if you are getting the information their also.
I'll recommend you to do the proper
testing and find out the state of session in each of these senerio.
[ September 28, 2007: Message edited by: subodh gupta ]