unfortunately the archive KB was discontinued yesterday :(
It sounds like the grid on the IT_ITEM screen is corrupted for that user. Have you tried just right clicking on the item maintenance and doing reset panel and reset all grids? I'm not certain that doing this would reset the grid in the IT_Item screen or not but it might be worth a try.
If that doesn't work it may require going into DFDM on the SY_GridDefinition table and look for a record in there for IT_ITEM grid with that user key. as always, make a backup of that table before you do anything in there. If your not familiar with the layout of that table and how records are stored I would familiarize yourself with that first. I think you would be looking for a record that starts with IT_ITEM. however, I tried to modify that grid for my user and it does not seem to be possible, unless you have added UDF's to that screen.