That often indicates an incomplete or damaged download file. Chances are the file you downloaded was incorrect on the OpenOffice server, it happens occasionally, or given your download speed a problem that occurred during the download. Downloading OpenOffice again will be painful with your download rate, but that is probably what you will have to do to "fix" the problem and there may be other hidden problems you have not found yet.

If we knew what it was we were doing, it wouldn't be called research, would it?

— Albert Einstein