Error when adding to an EndPoint in new management portal

Now that I am being forced to use the new Azure management portal, it seems that I am unable to add an EndPoint. I have 5 IP addresses in my ACL (added using the old management portal), and when I try to add a sixth (using the new management portal) I get an error:

Failed to update endpoint on virtual machine 'VM Machine Name'. Unable to create virtual machine 'VM Machine Name': 'The value for parameter 'EndpointAcl.Rules.Rule.Order' is null or empty.'.

I have tried entering a value in the "Order" field, and also I have tried to delete the value.

Is this a bug?