Fatal installation problem on a regular LAMP setup

After downloading, extracting the files and modifying the wp-config.php (no extra whitespace there, trust me) I headed for the wp-admin/install.php.

On the top I get the warning:
Warning: call_user_func_array(): First argumented is expected to be a valid callback, ” was given in /home/customers/ilmiantajat/public_html/testing/zuni/blog/wordpress/wp-includes/functions.php on line 1268

And after that, of course, a regular header warning (most likely caused by the warning abocve):
Warning: Cannot modify header information – headers already sent by (output started at /home/customers/ilmiantajat/public_html/testing/zuni/blog/wordpress/wp-includes/functions.php:1268) in /home/customers/ilmiantajat/public_html/testing/zuni/blog/wordpress/wp-admin/install.php on line 16

The stuff below shows fine, and I can continue to give my blog name and email address (showing the same warnings on top), but finally on “Now we’re going to create the database tables and fill them with some default data.” I get a slew of warnings like:
Warning: preg_match() expects parameter 2 to be string, array given in /home/customers/ilmiantajat/public_html/testing/zuni/blog/wordpress/wp-admin/upgrade-functions.php on line 462

Any help?

I have tried granting full (777) permissions to the wordpress directory, have made sure that the files are owned by the correct user/group and so forth. The system is a regular LAMP setup that I have full control over, and has worked perfectly well with many apps before.