I got the "security" to accept after a few tries, but then it told me I couldn't download and to check if my browser supported Javascript. This is using Firefox 3 with javascript enabled.
So, I figured I'd try it with internet explorer, and after I screw up the code the first time, it tells me I have entered too many wrong codes
Seems their "security feature" is a transparently BS attempt to get people to buy premium accounts by making it impossible to download without one.
Could you upload it on a different site? Maybe megaupload.com, I've been able to download files from there without much hassle.