After editing a table in Impress and setting the border style (referred to as
the line style in the “Format Cells” dialog), trying to set it back to “None”
from the table formatting toolbar does not work.

Steps to Reproduce:

1) Create a new empty presentation in Impress.
2) From the “Insert” menu, choose “Table…”.
3) Click “OK” to accept the default number of rows and columns.
4) Using the “Borders” popup (on the top row of the table toolbar to the left of
the color dropdown list), select the border that includes all internal and
external edges (the last option in the bottom right of the popup). The first
cell of the table should have a thin black border.
5) From the “Border Style” popup, click “None”. The border on the cell should
disappear, but instead it remains visible.
6) From the “Border Style” popup, click on any border style except “None”. The
border will change, as expected.

It is possible to set the border style back to “None” using the “Format Cells”
dialog, as described below.

1) Open the “Format Cells” dialog by clicking properties button in the table
formatting toolbar (bottom row, leftmost button).
2) On the “Borders” tab, select “None” in the line style selection list, then
click "OK". Note that this seems to set the actual border to none as well as the
border style.
3) Attempt to set the border style to something besides “None” from the table
formatting toolbar. It will have no effect until the number of border lines is
again set.

This behavior is consistent on single cells, selected groups of cells, and on
the whole table. It is most easily seen with the steps described above, but any
type of border will cause it to occur.