Empty query string if containing letters

Hi,
I'm getting desperate since upgrading my local machine to apache 2.2.4 - a
..htacess/"modrewrite" runing perfectly on my webserver (apache 1.3.33) won't
run with my apache 2.
The bizarre thing - it runs if the $1/q1-query string only contains numbers
and the "-", but it won't run if it contains any letters.

Example: The .htaccess is like:
---
RewriteEngine on
Options FollowSymLinks
RewriteCond %{QUERY_STRING} test=([a-zA-Z0-9\-]+)
RewriteRule ^listing\.php$ site_%1.htm? [R=301,L]
RewriteRule ^site_([a-zA-Z0-9\-]+)\.htm$ listing_2.php?test=$1 [L]
---

If the URL is like site_23-12.htm - it runs perfectly.
BUT:
If the URL ist like site_a.htm - it gets an empty query string.

What mistake I'm doing?
(sorry for my poor english - I'm German and a newbie to apache-webserver's)

Thanks for ANY help!

Frank