Index: wp-includes/class-wp-admin-bar.php
===================================================================
--- wp-includes/class-wp-admin-bar.php	(revision 19396)
+++ wp-includes/class-wp-admin-bar.php	(working copy)
@@ -150,6 +150,8 @@
 				$class .= ' ie7';
 			elseif ( strpos( $_SERVER['HTTP_USER_AGENT'], 'MSIE 8' ) )
 				$class .= ' ie8';
+			elseif ( strpos( $_SERVER['HTTP_USER_AGENT'], 'MSIE 9' ) )
+				$class .= ' ie9';
 		} elseif ( $is_iphone ) {
 			$class .= ' mobile';
 		}
Index: wp-includes/css/admin-bar.dev.css
===================================================================
--- wp-includes/css/admin-bar.dev.css	(revision 19396)
+++ wp-includes/css/admin-bar.dev.css	(working copy)
@@ -439,6 +439,11 @@
 	margin-top: 1px;
 }
 
+#wpadminbar.ie9 #adminbarsearch .adminbar-input,
+#wpadminbar.ie9 #adminbarsearch .adminbar-input:focus {
+	background-color: #fff;
+}
+
 #wpadminbar #adminbarsearch .adminbar-input:focus {
 	color: #555;
 	text-shadow: 0 1px 0 #fff;