diff -up plugin.orig/category.rb plugin/category.rb
--- plugin.orig/category.rb	2009-08-22 10:35:42.000000000 +0900
+++ plugin/category.rb	2009-08-22 10:48:46.000000000 +0900
@@ -4,6 +4,7 @@
 # Distributed under the GPL
 #
 require 'pstore'
+require 'kconv'
 
 #
 # initialize
@@ -236,7 +237,9 @@ class Info
 		@cgi = cgi
 		@years = years
 		@conf = conf
-		@category = args[:category] || @cgi.params['category']
+		@category = args[:category] || @cgi.params['category'].map {|c| 
+			::Kconv.isutf8(c) ? c : @conf.to_native(c, @conf.encoding_old)
+		}
 		@year = args[:year] || @cgi.params['year'][0]
 		@month = args[:month] || @cgi.params['month'][0]
 		@mode = :all