I have a client with 400 and I am manually entering them and clicking edit>and changing the next date manually. Something is obviously broken here. What a pain in the neck.

You are correct, the next date is not advancing and I don't want to leave it to chance that they don't suddenly send out and I have duplicate invoices and a much bigger mess to clean up and angry customers. @Anonymous do you know of any resolution or can you let the developers know of this issue?