Upgrading error from beta 23 to 25

[محروم.كوم]

Hi all.
I've deleted install.php and renamed other 2 files like you upgrade guide.
Upload every /upload files directory.
When I run http://www.***.it/core/install/upgrade.php I complete the form for config.php and click on "create files".
After this it answer with:

Warning: file_get_contents() [function.file-get-contents]: Filename cannot be empty in /home/vitainca/public_html/core/install/makeconfig.php on line 237

Error - Could not open frontend config file.

What can I try to do ?

Thanks,
Andrea __DEFINE_LIKE_SHARE__