1. Open the wp-includes/template-functions-category.php file in a text editor like Wordpad.
2. Go to around line 103 where it says get_the_category_by_ID.
3. Create a new line after that and paste in $cat_ID = (int) $cat_ID;
I thought I placed this in correctly and now that I see what has happened (http://visibleh20.com/WordPress/) I wish I hadn't.
What should I do?