Diagnosis
In master data maintenance for the asset, you have entered aquantity, but you have not entered a unit of measure.
The asset cannot be managed with a quantity if the the unit ofmeasure is missing. In particular, it is not possible to enterquantities when posting.

Procedure
Enter the unit of measure. If the field for the unit of measuredoes not appear on your screen, or it is not ready for input, this isdue to screen layout rule &V1& in your master record.
In this case, you first have to end the master data transaction, andchange the screen layout &V1& in Asset Accounting Customizing.