unable to create Reversal GRN

Hi

My user is unable to do the reversal GRN for a PO. Because it shows the **** in units columns of GRN screen.

When I click on the GRN in PO history tab in PO the error come as u201Cunit *** is not created in language ENu201D.

So what is the problem .kindly suggest with your helpful inputs.thanks in advance

Regards

sss