Index: rewrite.php
===================================================================
--- rewrite.php	(revision 14237)
+++ rewrite.php	(working copy)
@@ -1564,9 +1564,10 @@
 		if ( empty($this->permalink_structure) )
 			return $rewrite;
 
-		// robots.txt
-		$robots_rewrite = array('robots\.txt$' => $this->index . '?robots=1');
-
+		// robots.txt - this is only needed if wordpress is installed at the root of a domain
+		$home_path = parse_url(home_url());
+		$robots_rewrite = ( !isset($home_path['path']) || $home_path['path'] == '/' ) ? array('robots\.txt$' => $this->index . '?robots=1') : array();
+			
 		//Default Feed rules - These are require to allow for the direct access files to work with permalink structure starting with %category%
 		$default_feeds = array(	'.*wp-atom.php$'	=>	$this->index . '?feed=atom',
 								'.*wp-rdf.php$'		=>	$this->index . '?feed=rdf',