If you normally don't have problems installing software and you do it regularly, it suggests that the problem is with what you are trying to install, not your computer. Most of the time, that error message is correct. If there is a problem with the installation file, you don't want to start doing exceptional measures to make it load. That's just asking for trouble.
Two things pop to mind that I would start with. First, sometimes there is a problem with the installation file, itself. Second, sometimes the download is incomplete or gets corrupted. I would try downloading it again, preferably from another source, if possible. Double check that the download was complete and successful. Then try to install it. If you still have...