I'm sorry to hear that you were having difficulty loading your event's invitaitons. We've had some reports of other users experiencing the same trouble within their IE browsers.
Could you try the following:
If that works, close that IE window and open a brand new one normally.
Then you will want to click on Tools > Manage Addons and disable them one at a time until the product works..
Another fix that we found was clearing your cache/cookies in your browser.
Please let us know if any of those help to resolve this for you.