White space that I can't select (AutoCAD LT 2009)

I've inherited a drawing from a previous employee. A table was drawn manually (i.e. the coloured cells are areas where rectangles have been used with hatching). This is shown below:

I've tweaked the table to add more cells but when I do this, there appears white (as shown) which I can't select in order to remove. When I try to select it, I use the selection mode shown below - i.e. select everything in the box.

Please can someone advise how to deal with this?

Here are the layer properties:

Thoughts welcome. I can post back with what happens when I try out suggestions.

I have moved both of your recent threads to the Autocad LT section. In the future, please post your LT questions there.

Could the white space be a wipeout and could its frame be turned off?

Maybe when you add cells it messes up the hatch somehow? Have you tried redoing the hatch to see if it fixes the issue?

To add to what ReMarek mentioned it may also be a background mask from text where the width has not been adjusted accordingly.

Could the white space be a wipeout and could its frame be turned off?

This works. Thank you

Another amazingly lucky guess.