Installing on localhost: DB problem

I installed Zen Cart many times on my local machine under Lampp before.
I recently upgraded to Jaunty. Installed Lampp, which runs fine. When I try to install Zen Cart, the installation process always stops after I input my db-data. The page ist zc_install/index.php?main_page=database_setup. Opera tells me that this site is not available.
DB exists, password is correct. I have no idea what it could be. Never had this problem before.
Somebody got any idea?

Have you at least checked your services to make sure that your apache (or apache 2) is running?

then open up a terminal and go to your web root

cd /var/www/ 

do a ```php
ls

then ```php
 cd /etc/php5/
cat php.ini

(vi php.ini) if you're careful

look to see what you're error reporting is on

You should at least get a site up with some errors if you're having DB connectivity problems, if not ~ you haven't installed correctly

Thank you for your answer.
Apache is running. Otherwise I would not be able to access via localhost. If I input wrong data, I get the error screen, which is correctly. If I input the right data, I get an error from the browser:

Connection closed by remote server

You tried to access the address http://localhost/zencart/zc_install/index.php?main_page=database_setup, which is currently unavailable. Please make sure that the Web address (URL) is correctly spelled and punctuated, then try reloading the page.

I installed it often on other machines successfully.

I found the problem.
Before I used an older version of LAMPP. The new version (1.7.2) I tried now uses PHP 5.3 which does not work with zencart.
Version 1.7.1 of LAMPP works fine.