Using your page source I was able to construct the stream url and download without even being a member. It's an encrypted rtmp stream (RTMPE) so you'll need a tool capable of grabbing those specific types of streams. I did my test with the first video on the front page, #118 Paula.
Her member video urls look like this:
rtmpe://64.59.67.50/content/mp4:BIP/BIP_118_Paula/BIP_118_Paula-FLV-Low-01.f4v
or
rtmpe://64.59.67.50/content/mp4:BIP/BIP_118_Paula/BIP_118_Paula-FLV-High-01.f4v
Now the method I used will be a little different obviously since I'm not a member, but you can try using Streamtransport to grab the vid as it plays or rtmpdump using the above urls as your guideline.
Happy downloading
p.s. here's the low version I used for a test of paula if you want it:
http://www.megaupload.com/?d=Z7FYZ03W