[support] Turning off multibyte support?

I just installed drupal 5.1 on a web hosting provider. When I try to run install.php, I get the error:

Incompatible environment

The following error must be resolved before you can continue the installation process:

Multibyte string input conversion in PHP is active and must be disabled. Check the php.ini mbstring.http_input setting. Please refer to the PHP mbstring documentation for more information. (Currently using Unicode library Error)

It is unclear what I'm supposed to do to fix this. I don't see any php.ini string anywhere in my site directory tree. I'm assuming this is some system global config file (which I don't have access to).

-- roy@panix.com