I've just went through the update process from 1.1.4 (full installation) to 1.2 and the only error I encountered was related to outdated version of discontinued module. (if that's the case for you, you can grab the compatibility pack from here: click).
This error did not, however, interfere with the core of upgrade process and the upgrade went through. I had to restore theme files manually thou. To do this, enter the following address:
http://<your_epesi_address>/admin/themeup.php
It may ask you for credentials, just use your super admin login. After that your installation should be working, even without the compatibility pack.
Still waiting for any error message you may find in error log.
Also, please tell me if refreshing epesi main site asks for an upgrade again, simply starts epesi or perhaps throws an error immediately.
Kind regards,
Arek
