there should be no difference as when you run the payroll, you enter the hours as you wish - this would have no effect for the update. You can pay your staff by the hour or salaried or a mixture, depends on how you set up your system.
are you trying to update for a period that is included in a previous update perhaps?
I've changed them all to monthly now. The last pay run update was done yesturday but as 4 weekly. This was for tax month 6. The next pay date is Oct 28th which is tax month 7.
If I advance the date to Oct 28th, it won't allow me to input a payment for any of them... I'm just worried that when it gets to the day itself, it still won't let me enter payments...