It seems that sorting on a column in a Grid does not work as I would expect when some of the cells in the column are empty. I have a Grid in which some of the fields are only populated for some rows. Sorting on columns with data in every row works fine, but when I sort on the columns with patchy data, the rows do get re-ordered, but in an apparently semi-random fashion, with the blank values scattered through the column, and even the rows with real values not ordered in any obvious way.

i) is this a known problem? (I searched but couldn't find anything.)