.htaccess for cakephp

I'm trying to get a CakePHP application to work. For this, I've set up a brand new Debian installation, updated the configuration and put everything in /var/www, which has the following content:

app
cake
.htaccess
index.php
vendors

The .htaccess file contains the following:

<IfModule mod_rewrite.c>
    RewriteEngine on
    RewriteRule    ^$    /webroot/ [L]
    RewriteRule    (.*) /webroot/$1 [L]
</IfModule>

If I access my virtualhost (http://myhost/) I see the correct page. But even the JavaScript loaded with src="/js/validate.js" fails (it's located within /var/www/app/webroot/js/validate.js):

[Wed Aug 26 15:45:12 2009] [error] [client 10.7.10.52] Request exceeded the limit of 10 internal redirects due to probable configuration error. Use 'LimitInternalRecursion' to increase the limit if necessary. Use 'LogLevel debug' to get a backtrace.
[Wed Aug 26 15:45:12 2009] [debug] core.c(3063): [client 10.7.10.52] r->uri = /webroot/webroot/webroot/webroot/webroot/webroot/webroot/webroot/webroot/webroot/js/prototype.js
[Wed Aug 26 15:45:12 2009] [debug] core.c(3069): [client 10.7.10.52] redirected from r->uri = /webroot/webroot/webroot/webroot/webroot/webroot/webroot/webroot/webroot/js/prototype.js
[Wed Aug 26 15:45:12 2009] [debug] core.c(3069): [client 10.7.10.52] redirected from r->uri = /webroot/webroot/webroot/webroot/webroot/webroot/webroot/webroot/js/prototype.js
[Wed Aug 26 15:45:12 2009] [debug] core.c(3069): [client 10.7.10.52] redirected from r->uri = /webroot/webroot/webroot/webroot/webroot/webroot/webroot/js/prototype.js
[Wed Aug 26 15:45:12 2009] [debug] core.c(3069): [client 10.7.10.52] redirected from r->uri = /webroot/webroot/webroot/webroot/webroot/webroot/js/prototype.js
[Wed Aug 26 15:45:12 2009] [debug] core.c(3069): [client 10.7.10.52] redirected from r->uri = /webr