I knew it had to be something like that. But I tried your fix, a la

use strict;
use Win32::OLE qw( in );
use Win32::OLE::Const 'Microsoft Word';

my $filename = 'E:\test.doc';

my $word = Win32::OLE->new('Word.Application', 'Quit');
my $doc = $word->Documents->Open($filename) || die("Unable to open doc
+ument ", Win32::OLE->LastError());
my $nwords = $doc->Words->Count;

my @wordtext;
my @wordcolor;

my $starttime = time;

my @items = in $doc->Words->Items;

for(my $i = 1; $i <= $nwords; $i++)    {
    $wordcolor[$i] = $items[$i]->HighlightColorIndex;
    $wordtext[$i] = $items[$i]->Text;
}
[download]

and @items comes back null.