Many thanks for sharing the ppt files with me, we really appreciate it. I was able to reproduce the problem (it seems the files don't quite match the official specification for some reason, we have 10,000+ .ppt files that open fine but your ones definitely don't!).
I've been able to make a fix, which should be in the next release. If you like I can give you access to a beta release of the new version using Apple's testflight service?