This Ubuntu file-dialog related issue has been reported several times. We couldn’t reproduce the crash in an Ubuntu, but on Debian Linux there was no file-dialog related crash ever for us. Here you can find the related posts, in the end it turned out to be an Ubuntu/system-related system issue, exact cause and what the solution was for this user is unknown yet:
Maybe a look at Ubuntu forums can reveal some Nautilus file-browser issues with certain filetypes, etc:
You can try other filebrowsers, like PCmanFM, etc.