We're sorry for any inconveniences caused, the reason this is happening is; you may be creating items within a list(s) you had prior to the upgrade. What you'll need to do is swipe left on the list in question and select "edit" then choose "due date". You'll then need to select "App Default" or a date of your choosing for the due date for those lists.
Lists created in the new version of Todo Cloud will automatically have the default due date you've chosen within settings applied to them.
Sorry to hear about the troubles. Are you creating these tasks from the App's main list screen or within a specific list?