I dimly recall running into a similar problem some years ago - I don't remember what the server type was (I don't think it was IIS), but the forms in the script worked fine with one server and had a similar kind of POST/GET confusion with another. I solved the problem by making 'POST' the default method for the entire script rather than just defining it in the form.

(I was rather hesitant about posting this, because I realize that it sounds like voodoo; it shouldn't have interfered with anything, or fixed anything. However... it fixed the problem, is still working a number of years down the road, and has not caused any problems on a variety of servers where it's been used. Sometimes, especially when a client is breathing down the back of your neck _and_ counting minutes/pennies, this kind of Band-Aid is the best you can do. :-[ )

Demonstration of how this works:

#!/usr/bin/perl -w
use strict;
use CGI qw/:standard/;
$|++;

print header, start_html, $ENV{REQUEST_METHOD}, end_html;
[download]

GET
[download]

...
$|++;
$ENV{REQUEST_METHOD} = 'POST';    # Added this line
...
[download]

Output:

POST
[download]