There could be numerous reasons, and I'm almost definate that it's not the WinRar itself.
It could be that the hack was not fully downloaded, this could be because of an internet problem or the download itself could be damaged.
Another reason could be if the file needs the password and you're clicking OK or Cancel which automatically disregards the file.
I can only recommend downloading the file again, as the only understandable reason is the incomplete download or corrupt file.