How to fix an error message on a multisite install?

It’s a fresh multisite install. There’s no other plugin installed except for multidb.

I think I followed all the steps correctly. When I logged back in it gave me the following errors:

Warning: mysql_set_charset() expects parameter 2 to be resource, boolean given in /home/server/public_html/wp-includes/wp-db.php on line 650

Warning: Cannot modify header information – headers already sent by (output started at /home/server/public_html/wp-includes/wp-db.php:650) in /home/server/public_html/wp-includes/option.php on line 568

Warning: Cannot modify header information – headers already sent by (output started at /home/server/public_html/wp-includes/wp-db.php:650) in /home/server/public_html/wp-includes/option.php on line 569

When I tried to create a new site manually, it gives me the following error:

Warning: mysql_set_charset() expects parameter 2 to be resource, boolean given in /home/server/public_html/wp-includes/wp-db.php on line 650

Warning: Invalid argument supplied for foreach() in /home/server/public_html/wp-content/db.php on line 281

Warning: Cannot modify header information – headers already sent by (output started at /home/server/public_html/wp-includes/wp-db.php:650) in /home/server/public_html/wp-includes/pluggable.php on line 876

The sites that I manually created will then appear on the list of sites in the network. But when I go to one of them, it gives me an error message.

Warning: mysql_set_charset() expects parameter 2 to be resource, boolean given in /home/server/public_html/wp-includes/wp-db.php on line 650

Warning: Invalid argument supplied for foreach() in /home/server/public_html/wp-content/db.php on line 281

Warning: Cannot modify header information – headers already sent by (output started at /home/server/public_html/wp-includes/wp-db.php:650) in /home/server/public_html/wp-includes/pluggable.php on line 876

You can see the same thing if you go to one of the sample sites: http://samplesite.momoblogs.com/

The front-end of the main site is giving the following error message:

Warning: mysql_set_charset() expects parameter 2 to be resource, boolean given in /home/server/public_html/wp-includes/wp-db.php on line 650

Please help!