drupal.js in 5.x causes 15s delay in initial page load on XP IE7 and IE8

I'm not sure why I'd never noticed this before, but can reproduce at will with any 5.x site I know of. When opening IE7 or IE8 and visiting a Drupal 5.x site for the _first_ time, there is a 15s delay from requesting to receiving - and parsing - drupal.js. This effectively causes the site to stop dead in its tracks until this file is processed. I have tested this on everything from 5.8 -> 5.18 and can reproduce everytime. I used HTTP Sniffer (http://www.effetech.com/sniffer/) to determine where this speedbump lies.

This appears to be specific to XP, sites load without issue in Vista, and where it is 5.x I'm not sure how much traction, if any, this will get. I'd venture to guess that the issue is more something in XP, but leads to a poor user experience on sites who may not be willing to shell out money to upgrade to 6 or 7 :).