"Your browser sent a request that this server could not understand."

Hi,
In order to map the websites I develop locally easily I set up Apache
mod rewrite tomap a url to a directory. Thsi way I do not have to make
a Virtual directory for every project but the URL is being rewritten
to map a directory on the local system. Here's the setup:

I set up an A record in the DNS of my domain to point back to the
local machine wjenI use a special prefix in the URL:
*.local 127.0.0.1
(saying "every subdomain ending with .local is to be redirected to
localhost)

I set up Apache's httpd.config Mod Rewrite like this:

LoadModule rewrite_module modules/mod_rewrite.so
(remove the comment - # - sign)

RewriteEngine on
RewriteCond %{HTTP_HOST} (.*)\.local.mydomain.com
RewriteRule (/.*) D:/www/wwwroot/%1/$1
(saying: every request ending on local.mydomain.com has to be rerouted
to the directory D:/www/wwwroot/<whatever
preceded .local.mydomain.com>/<whatever followed.local.mydomain.com)

This worked fine: if I had a directory "d:/www/shipyards/q.cfm all I
had to enter in my address bar was "http://
shipyards.local.mydomain.com/ q.cfm and q.cfm was served.

Until yesterday, the same url (http://shipyards.local.mydomain.com/
q.cfm) only gives me this response
---------------------------
Bad Request
Your browser sent a request that this server could not understand.
---------------------------
Apache_error log gives this:

[Sat Jun 14 13:29:10 2008] [error] [client 127.0.0.1] Invalid URI in
request GET / HTTP/1.1
[Sat Jun 14 13:29:20 2008] [error] [client 127.0.0.1] Invalid URI in
request GET /q.cfm HTTP/1.1

Apache access log gives this:
---------------------------
127.0.0.1 - - [14/Jun/2008:13:29:10 +0200] "GET / HTTP/1.1" 400 226
127.0.0.1 - - [14/Jun/2008:13:29:20 +0200] "GET /q.cfm HTTP/1.1" 400
226
---------------------------

I have no idea why the web browser doesn't recognize these requests
anymore and there is nothing that comes to mind I might have changed
that caused this behaviour. I tried setting up Virtual Hosts to
circumevent the problemn but there Apache won't start for other errors
in the config file. And actually I want the situations with Mod
rewrite back as before.
Can anyone here help me out?

Thanks!

Windows XP SP2
WAMP Server:
Apache 2.2.8
FireFox 2.0.0.14 / IE 7.0.5730.13