When I am on .com I always get a little alert in internet explorer ( on the bottom right of the taskbar, a little eye with a no-entry sign, if memory serves) When I click on the icon it takes me to the ie cookies/security level box and I am informed that my cookies setting is too high for that site( it is set to medium) Obviously IE dosn't like something that the .com site is doing with cookies.
Hope that the above makes some sort of sense