Even after the payment has cleared (upwards of 10 days for e-cheques), Paypal will hold the payment for 21 days against your performance as a seller.
Do not ship until PP tells you the payment has cleared. Ship promptly after it has cleared. The money will be waiting" in escrow" and you will get it, eventually.
Meanwhile send a nice note to the buyer thanking him for his e-cheque payment and telling him that his item is packed and ready to ship as soon as PP clears it and allows you to print a shipping label . Which they won't until the cheque clears, btw. And when it does, contact the buyer again to let him know the item is on its way.