Try replacing the action on the form with a simple CGI parameter dumper like this:

#!/home/crossda/perl/bin/perl

use strict;
use warnings;

use CGI ':cgi';

print header(-type => 'text/plain');

foreach (param) {
  print "$_ : ", param($_), "\n";
}
[download]

You'll see that Firefox sends parameters called "page.x", "page.y" and "page". IE doesn't send the "page".

You'd need to check the specs, but I suspect that IE is doing all it's supposed to do. The extra parameter from Firefox is useful but (I think) non-standard.