Subject: Re: Retrieving Historical price Data
It takes 1-2 seconds for the page to stabilize.
I suspect WSH and the like would have trouble with this.

WSH and other scripting languages have a Sleep (or equivalent) command. Send the URL request, followed by a sleep for 10 seconds before continuing. It's slow but just let it run overnight. Just set the number of seconds high enough that it always works. (If it fails, restart the download at the stock that failed, then merge the two files.)