Data error when running Codeunit 104048

Yet again I am running an upgrade and again I have come across an error I have never encountered before.[:(!] When I run codeunit 104048 it generates an error - item ‘9616’ does not exist.[xx(] The error always occurs when the codeunit is running through the Purchase Line table. We have checked our item table and the item does exist. Can anyone tell me what conditions an item would have that would make the codeunit fail at this point? We have run the debugger and the problem seems to be in the UpdatePrice trigger of the codeunit if that is of any help to anyone. Any help/suggestions would be gratefully received.