Quark table missing cells

[bookcrone]

I designed a table today in Quark 6.5 and ended up with what looks like two missing cells at the bottom right of the table. I say missing because I can't select them. They look like cells that have been "lost" and replaced by diagonal dashed lines, one per cell. Please, what are they, how did I get them and most of all, how can I get rid of them? Even when I try to select the entire row (one wide combined cell and the two "missing" ones) the delete option is not available in the Tables choices.
bookcrone