I had the same problem, sucks to know it's Bitdefender blocking. As much I love their databases and small resource footprint, their lack of customization options really irks me.
We can submit it to Bitdefender's false positive submission page:
http://www.bitdefender.com/site/Main/automaticSampleUploader/The URL to claim as false positive is
http://dl.dropbox.com/---
I have been trying out Qihoo 360 for some customers of mine and despite the company's main revenue coming from advertisements (and all apparently in China), it seems to be a great free solution. In full security mode, it will also use Bitdefender and Avira's engines for scans.
I still recommend buying Kaspersky Internet Security for anyone willing to pay, though.