session variables mysteriously disappear in IE7?

I can't login to our Rails 2.3.8 application any more since a recent update to Windows. This is IE version 7.0.5730.13.

In my login controller, we authenticate the account and put the user AR in 开发者_StackOverflowsession[:user], then redirect to a main menu.

However, the redirect fails, because when the main menu controller checks to see if the user is logged in, session[:user] is now nil!

Please note this works fine in Firefox and Safari.

HELP!!!

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Check your cookies configuration. It seems something related.