Error when a user with a blog creates another

When a new user creates a blog, everything goes well.

When a user with a blog creates another blog I get the following message:

Warning: fopen(/home/clicksty/public_html/wp-content/plugins/EMPTY) [function.fopen]: failed to open stream: No such file or directory in /home/clicksty/public_html/wp-includes/functions.php on line 4339

Warning: fread(): supplied argument is not a valid stream resource in /home/clicksty/public_html/wp-includes/functions.php on line 4342

Warning: fclose(): supplied argument is not a valid stream resource in /home/clicksty/public_html/wp-includes/functions.php on line 4345
The site one is yours.

Eventhough I get this error the site is created.

What is going wrong here? I had the setup by the WPMUDev.org guys.