How can I make two browser windows share the same "session"?

Question

I have an app that needs to open a new window (in the same domain) so the user can view a report, but on some browsers* the new window doesn't share the non-persistent cookie of the original window, which causes the user to have to sign in again. Is there anything I can do to stop the user having to sign in again in the new window?

*In fact, in IE7 it is sporadic - sometimes new windows share cookies, sometimes not.

Answer 1

I thought IE7 shared non-persistent cookies with tabs in the same window, as well as windows that were generated from the current window (whether or not this is the same for manual opens like File->New, or programmatic script opens, I'm not sure), but that fresh instances did not.

Firefox shares them across all windows, regardless of how they were opened. I've always assumed that this is just the way it is, and you'd have to use persistent cookies, cookie-less sessions, or develop a single sign-on/ticketing mechanism to work around it.