I am terribly sorry for the trouble. It turns out that the TwentyTen theme's functions.php is TOTALLY different from others.
I think you would OK after deleting all the code I supplied. If not, replace functions.php with a fresh copy from a new download of WP 3.0. If you don't want to do that, I can email you a copy if you email me at mmcdonaldky =at= gmail.com.
Once you are working again, it would be wise to create a child theme of TwentyTen to hold your changes. That is really easy to do:
- Create a new folder in the themes folder - call it twentyten-child.
- Copy the file below into twentyten-child/style.css.
- Go to Admin->Appearance->Themes, and activate the child theme.
Now, any changes you make can be to the child, leaving the parent untouched.
Put the code I showed earlier into a new functions.php in the child folder and give it a try.
Again, very sorry for the trouble.
Theme Name: Twenty Ten Child
Description: Child theme for the Twenty Ten theme
Author: Your name here