iPad Keynote crashes on import of ppt/pptx files

When I import .ppt or .pptx files through iTunes on my Keynote app, Keynote goes blank and returns to the iPad home screen every time. I try importing the same files through dropbox, Keynote gets the same issue.It might be related to the size of the file or the file is password protected. I end up breaking up a large presentation into 2 files and it works.