Cannot Upgrade 2.4.1->2.4.2

I have using this guestbook around 2 years. And have update the system many time without any error

When I update the 2.4.1 to 2.4.2. After success update it's a blank page.

Here is my step, any error?

1) Unzip the 2.4.2 to 2.4.1 directory. Allow All overwrite the file
2) Copy the orginal 2.4.1 config_inc_php to 2.4.2/admin folder to overwrite the file
3) Run the misc/update_db.php (It's show nothing to require update)
4) Run the guestbook. http://www.domain.com/guestbook

It's found a blank page!

I have change all the attribute to 777 and change the tmp/public to 777 also have this error!

Any user have this problem?