I'm unable to send any MRO without a payment ID using your GUI even though, as I understand it, a payment ID is not a requirement.
Are you referering to my wallet? You can just leave the payment ID field empty if you don't want to include the payment id.
Actually no, but so far all of my attempts to send monero using your GUI have failed. If I leave the payment ID blank it gives me the error message that the Payment ID is in the wrong format. If I fill it in, then it tells me the payment address is invalid.