Problems setting a communication strategy.

Hi everybody.

In order to be able to send a purchase order vía fax -through a third-part software- I need to change the communication strategy in customizing. So I've navigated to the proper tree and when I try to put a new position in the comm strategy, I've got the message TK455 which tells me that I need to fill the position with numeric fields (thing I'm already doing).

SAP insists that the error is due to a functional error of our own (????)

HAs anybody ever got the same problem?

Thanks for your helping.