Matthew1980 - 10:53 pm on Dec 15, 2011 (gmt 0)
>>The session is probably dependent on a cookie being set in the browser.
Ensure that ALL browsers have permissions/abilities to set cookies/sessions - as essentially they are both the same thing.
Also, put some code in to varify that cookies/sessions have been set as expected, or just pop a friendly message on stating that your site requires cookies/sessions turned on in order to function.
Hope that makes sense.