Invoice can't be cancelled

Hi Guys:

           I activate the invoice print out automatically, it works, but I find the Invoice can't be cancelled after that.

           When I save the cancellation , 'Update was terminated' , I check the system log,the error message is that 'the invoice has been cancelled, you can't print it'.  In billing output condition record, 'print date/time' was set to '4 send immediatelly'.

           I think there shouldn't be  inconsistent for this.

           Is there any idea or expe for this?

           Thanks.

Stephen