Highlight problems with single post

Hi there! I’m trying to highlight my menu but I have a problem when I’m in a single post. If i go to (exampel) “Movie” -category then it works and gets highlighted but when I’m in a single post in “Movie” then my link doesn’t get highlighted. Here’s my code:

<li<?php
if (is_category('movie') || in_category('3') && !is_single())
{
echo " id=\"current\"";
}?>>
<a href="<?php bloginfo('url') ?>/show/movie">Movie</a>

What’s wrong with this? Have patience with my English, I’m Swedish ??