Others may have had no problem with this, but I constantly seem to find issues with Yahoo hosting. Today I was having trouble upgrading to the latest version of Concrete5 on a Yahoo small business hosting plan with a memory_limit error. I fixed this by finding file.php in concrete/concrete/helpers and make sure the first two lines look like this

<?php
ini_set("memory_limit", "64M");

or whatever you want in place of “64M” - I noticed Yahoo seems to default to 20M.
Save the file and make sure your mysql account has INDEX privileges and you should be good to go. At least this worked for me.