You need to send it in smaller amounts. Keep lowering it until you are able to send it.

Basically your transaction is made up of lots of smaller transactions on the blockchain. There's a limit to how big a transaction can be at times. That's the only way I can explain it. It can also be caused by too much "dust" in your wallet. Too many small amounts of coins to combine together into a single transaction.

Just keep lowering the amount until you are able to send it in smaller chunks. It's just too many to send at once.