Purchase Order Entry - second line of item

Hi there,

I try to Purchase Order Entry and the first line is OK,
When I enter quantity with normal speed is ok,
but from second line and further if I try to write fast orders there is a bug, It change my quantity to 1.00.

note:
I'm using TAB to move from one box to another and the "Add Item" button I'm pressing with ENTER.

Thank you!