Problem with changing the unit price of a shipment while at AR invoi

has anyone else run into the problem of trying to change the unit price (and hence the total) of a shipment that you've pulled into to create an invoice at AR Invoice entry.

i change the unit price for one of the shipment lines. it seems to accept it, but when i hit save it reverts back to the original price.

i'm on 905.602.

any suggestions? is it a bug? do i have some type of setting wrong?