failure codeunit 21

Hello experts!

I have a question about an error that I get often about the posting date; NAV 2009 SP1, spanish date format dd/mm/yy

Allow posting from: 01/05/16
Allow ponting to: 30/06/16

Purchase Invoice, posting date 09/05/16

that invoice is impossible to post because of this error

Codeunti 21
CheckAllowedPostingDate(ItemJnlLine : Record "Item Journal Line")
WITH ItemJnlLine DO BEGIN
:
:
IF ("Posting Date" < AllowPostingFrom) OR ("Posting Date" > AllowPostingTo) THEN
Break on error FIELDERROR("Posting Date"
END;

I think it's a failure of NAV and I need to solve thank you for your help!