You're most likely right in thinking this is due to your IE settings. By default it doesn't look for a new copy of a page within the same session. You'll probably want to consider making a change to the page though, because the bulk of webbrowsers are probably using default settings.
There are a couple techniques you can use. You can place one or both of these meta tags in the page headers, which will tell the browser to request a new copy of the page each time. Another option is to add a dynamic variable to the querystring to ensure it's always different. For instance you might want to use something like:
&qrystr = &qrystr.'×tr='.time();
I'm not positive, but I think the unique querystring method might be a better choice if you want search engines to cache historical data. Guess that depends on your application.
<META HTTP-EQUIV="PRAGMA" CONTENT="NO-CACHE">
This directive indicates cached information should not be used and instead requests should be forwarded to the origin server.
<META HTTP-EQUIV="CACHE-CONTROL" CONTENT="NO-CACHE">
This directive has the same semantics as the PRAGMA:NO-CACHE. Clients SHOULD include both PRAGMA:NO-CACHE and CACHE-CONTROL:NO-CACHE when a no-cache request is sent to a server not known to be HTTP/1.1 compliant.