Session Issue in ASP.NET Web App

Hi,

We have developed web application (.net 1.1) and we are using sql server
2000 for state management and IIS 6.0.

We have different login screen in same Virtual Directory and the timeout is
different for both the screen. A user can access both the screens
simultaneously from same system using different IE instances(not using File
->New).
Still one session is overlapping other and vice versa, which is allowing one
user to access pages of other user which he is not intended to view.
This problem is not replicable all the time, sometime it happens.