well the problem shouldn't be your server-side code as it has nothing to do with the type of browser. Sessions aren't affected by the type of browser either.

Could you be a bit more specific about the error?

try crtl+f5 the thing in IE, it has some nasty cache habits now and then.

Hmm, neither IE nor FF sets session variables... That is on the server side... However if you're using session cookies to store varibles on the client side IE tends to fail updating the cookie. This is usually just a problem when you write code and the old cookie still is around in the browser cache. My simple solution is; clear the cookie storage in IE before trying out your updated code. Or exit the browser.