Various questions come to my mind here...(try to give more info so that i can help plz)
like, did you try to reboot ur comp so far?
what message does it give you more precisely as when you try to download?
have you your checked the internet security level? (open browser like I.e or Firefox go to"tools" then "internet options" (top of the page toward the question mark) check the level if it's set to top high then that may be the reason why)
have you installed/reinstalled a anti-virus/anti spyware? Those tend to block downloads from any website if set to high...
i can't tell more than that as it's all depending on your answers...for now i can't help you more...
