Keynote can't open specific keynote files

I have the recurring problem that Keynote is not able to open the files it created. It seems to be related to using specific line types.

I can work with the presentation a while and then the time to load the file will extend and extend and finally keynote won't open the file at all with the unhelpful message, that it can't open the file :-(

An example of such a file is here: https://dl.dropbox.com/u/3096725/images_20120817.key

Any idea what is going on here and how to deal with the issue?

Stefan