Hiya, Alex.
The good news is that buffering is in the delivery method of your video, not the encoder, so you did everything properly in Quicktime and won't need to go back and re-encode. :-)
The bad news is that (from your source code) it appears you're using Dreamweaver to embed your video. Unfortunately, this method doesn't allow for buffering of progressive downloads (like yours) but only files streamed from the prohibitively expensive Flash Media Server.
However, if you're up to the challenge, there are a couple of different workarounds to this issue (we're employing one of them here at the WebProNews Video Blog).
1) Build your own flv player with buffering built in. I wouldn't recommend this option, unless you have TONS of time on your hands and an exhaustive knowledge of Flash (or the willingness to learn).
2) Use one that someone's already built for you. There are a couple of free ones out there and even a couple that are open source (like
this one) which have this option.
Either way, this requires a bit more work (Dreamweaver's popular for a reason) but in the end, it's completely worth the effort.
Ciao and good luck with the site!