PO Organization Change

Hi,

I developed program for PO de-obligation and re-obligation which helps when company merger happens. I wrote a program to change the PO Organization.

It's working fine. But many a time, it gives an error message like:

Type Message UD Message

E ME Enter Shipping Instr.

I double checked the shipping instruction in PO, it's fine.

What would be the root cause?

Thanks for your help...:)