Error after moving WordPress installation

I am trying to move a WordPress site to a new server, but I cannot get it up and running on my local server (running XAMPP on OS X).

The site is running perfectly fine, but when I download the files, export the database and then hook everything up on my local copy, I get the following error message:

Warning: call_user_func_array() expects parameter 1 to be a valid callback, function 'twentyten_widgets_init' not found or invalid function name in /Users/Tim/Sites/coachhousetimbers.com.au/old/wp-includes/plugin.php on line 405

And the following when I try to access the site’s dashboard:

Warning: call_user_func_array() expects parameter 1 to be a valid callback, function 'twentyten_widgets_init' not found or invalid function name in /Users/Tim/Sites/coachhousetimbers.com.au/old/wp-includes/plugin.php on line 405
Warning: Cannot modify header information - headers already sent by (output started at /Users/Tim/Sites/coachhousetimbers.com.au/old/wp-includes/plugin.php:405) in /Users/Tim/Sites/coachhousetimbers.com.au/old/wp-includes/pluggable.php on line 934

Any ideas and/or suggestions?

I have moved many WordPress websites in the past and this is the first time I’ve seen this error. I am running WordPress 3.2.1.

Thanks!