Xampp: error 403 on Linux but not on Windows

Question

I have installed Ubuntu and XAMPP on my computer but when i start the web server and go to htt://localhost/webname (webname is the folder name inside htdocs) i receive error 403.

There .htaccess inside webname is the following:

# Created on: 03/01/2012
# Author: **********

# Redirect every request to index.php
RewriteEngine on 
RewriteBase /
RewriteRule ^$ /webname/public/index.php
RewriteRule ^about/?$ /webname/public/about.php
RewriteRule ^changelog/?$ /webname/public/changelog.php
RewriteRule ^home/?$ /webname/public/home.php
RewriteRule ^friends/?$ /webname/public/friends.php
RewriteRule ^(\w+)/?$ /webname/public/home.php?user=$1  
RewriteRule ^login/?$ /webname/public/index.php?show=login
RewriteRule ^signup/?$ /webname/public/index.php?show=signup
RewriteRule ^profile/(\w+)/?$ /webname/public/profile.php?user=$1

# Rewrite www.webname.com -> webname.com
RewriteCond %{HTTPS} !=on
RewriteCond %{HTTP_HOST} ^www\.(.+)$ [NC]
RewriteRule ^(.*)$ http://%1/$1 [R=301,L]

# Disable directory listing for all the subdirectories
Options -Indexes

On Windows everything works fine but on Ubuntu i keep receiving this error.

Thanks for helping.