This is not a template related issue, however....
I tested your site in Linux (Ubuntu 64bit) with Firefox, and Windows 7 64bit in IE8 and Firefox, and at no time did I experience any buffering. Keeping in mind that I am on a 30Mbit connection (which is much faster than most broadband connections), I used the Firefox Throttle plugin and throttled the speed down to 1.5Mbit (which is slower than most broadband connections) and still did not see any buffering on your site.