In some circumstances, Impress fails to save deletions properly, because having
deleted text from the presentation, it reappears after saving the presentation
and reloading it.

For example, try this:

1.  download http://www.aaa.net.au/campbell/BeautifulPhotos.odp
2.  open it in Impress and you can see that each slide has a picture with a text
box over the top - the text isn't part of the photos
3.  there are some performance problems editing the text in the document as
reported in http://www.openoffice.org/issues/show_bug.cgi?id=85551 but ignore
those for now
4.  on any of the slides, try clicking three times on the text and then
highlighting all the text with CTRL-A, then pressing delete so that the text
goes away
5.  now save the presentation
6.  close it
7.  load it back in

Actual Result:

I find that the deleted text is BACK after save/load even though I had deleted
the text.

Workaround:

I find that if instead of pressing delete to delete the text, I press SPACE
after highlighting the text, then this issue doesn't occur.