we're very sorry for the inconvenience, we are working on this issue and will notify you once it's been fixed.
Please note that it's only an issue with Internet Explorer and the regular web app. You can access all your tasks anytime using any other browser (Firefox, Chrome, Safari, Opera) or using the mobile site http://todoist.com/m (this version will work even in Internet Explorer).
we have fixed this issue and you should be able to access Todoist through Internet Explorer and the Outlook plugin.
We're very sorry for the inconvenience.