Can't install Drupal 8

Hello,

i'm trying a fresh install of D8 to see if i can help, but i can't even go past the installation process.

After unpacking, at step 1/7 and 2/7 i get the following warnings:

Warning: Invalid argument supplied for foreach() in Drupal\Core\Config\InstallStorage->getComponentNames() (line 138 of core/lib/Drupal/Core/Config/InstallStorage.php).
Warning: Invalid argument supplied for foreach() in Drupal\Core\Config\InstallStorage->getComponentNames() (line 138 of core/lib/Drupal/Core/Config/InstallStorage.php).
Warning: Invalid argument supplied for foreach() in Drupal\Core\Config\InstallStorage->getComponentNames() (line 138 of core/lib/Drupal/Core/Config/InstallStorage.php).
Warning: Invalid argument supplied for foreach() in Drupal\Core\Config\InstallStorage->getComponentNames() (line 138 of core/lib/Drupal/Core/Config/InstallStorage.php).
Warning: Invalid argument supplied for foreach() in Drupal\Core\Config\InstallStorage->getComponentNames() (line 138 of core/lib/Drupal/Core/Config/InstallStorage.php).
Warning: Invalid argument supplied for foreach() in Drupal\Core\Config\InstallStorage->getComponentNames() (line 138 of core/lib/Drupal/Core/Config/InstallStorage.php).
Warning: Invalid argument supplied for foreach() in Drupal\Core\Config\InstallStorage->getComponentNames() (line 138 of core/lib/Drupal/Core/Config/InstallStorage.php).

Then, after entering mysql details and clicking on "proceed" (http://www.example.com/core/install.php?langcode=en&profile=standard&op=...), the fun ends with a fatal error :(

Fatal error: Call to undefined function theme() in /path/to/core/includes/install.core.inc on line 941