When Quick Scan is used in Purchase Orders to lookup matrix items, some quantity entry cells are greyed out.

This indicates the dimension fields in the Item Matrix are not set up exactly the same (case sensitive).

For example if you have one item setup as:
Color - Black / Size - Large
and another setup as:
Color - BLACK / Size - Large
the system will recognize that both items are spelled the same so it will not try to create a double matrix grid in the Purchase Order.
However, the entries are not in the same upper or lower case, so the associated cells will not show as editable in a Purchase Orders.

To fix this, go to Database | Items | Matrices and locate the affected item(s). Edit the dimension fields to use the same spelling for related entries. Example: If most entries are labeled Small and one is SMALL, change SMALL to Small.

This issue has been filed as a problem report with Microsoft to be addressed in a future update. Until then remember that matrix cells are Case Sensitive.

Update: RMS users running the current edition of RMS should not experience this problem.