add rich:messages to your page
Added but no help.
The problem is:
At the first time, the page display with outputtext only. When I change the combo box to make the id !='0' at backing bean and re-render the panelgroup ppqty, at this time, the input field qty is shown and I input the new value on the qty and then click the submit, it can not get the new value at the backing bean!!!
When I removed the rendered attribute at the input field so that the filed is shown at all time, in this case, the submit function at backing bean can get the new value.
It seems that the rendered of the input field cause the backing bean cannot get the new value.
Is "bean" request-scoped? If yes, this won't work - search this forum for details. Use session, conversation (Seam) or keep-alived beans.