blank page at index.php?route=upgrade/upgrade

While trying to run the upgrade script on my WAMP (PHP Version 5.3.16, Apache 2.0 and MySQL 5.5.x) everything I get is a blank page. The error log in system/logs is empty and there are no error in apache logs. There is no output from $response->output();

I have a modified hosts file with http://www.testweb.local, everything is configured properly.
The site cant be loaded ate the moment because of missing columns in tables.
The upgrade havent got to the part where the tables are modified.

One problem might be, that the tables have no oc_ prefix, so the upgrade.sql might fail on order vs oc_order as its a reserved keyword and is not in `` in several places.

I've tried to to change it, but without success.
If I do a echo "test" at the end of the script, its returned properly in the browser. So the script had to finish one way or other.
error_reporting is set to E_ALL | E_STRICT

Upgrading from 1.5.1.3.1 to 1.4.1 (no vQmod)

Download OpenCart from here: http://www.opencart.com/index.php?route ... d/download. Don't download the ones with half done extensions and all at github.

Thats the version I've used for the upgrade...

Try uploading again. maybe you missed a file

Just a FYI to close this...
The 1.4.x version I've had was not finished yet, thus the blank page.