I was able to download and extract using both Windows XP built-in zip handling and 7-zip 3rd-party software.
What browser are you using? It works great with FireFox and Safari. I just tried with IE and the file downloaded corrupted. I'll have our hosting look into this. For now, my recommendation would be to use a standards-compliant browser like FireFox, Safari, or Opera until we find the proper incantation to make IE work.