Warning: call_user_func_array Help!

I am getting this error which seems to be preventing the them from loading up on my site:
Warning: call_user_func_array() [function.call-user-func-array]: First argument is expected to be a valid callback, ‘mytheme_add_admin’ was given in /home/public_html/site name/wp-includes/plugin.php on line 405

The site was working fine until this morning. I did update to the latest version of WordPress 3.2.1 and also did some updates to various plugins this morning which one of which probably started the issue.

I have disabled all plugins yet the error persists. I have even deleted the plug-ins that had been updated and re-installed and still have the error. Other themes load fine so I know it’s my theme, I just don’t know how to fix it.

Line 405 in plugin.php looks like this:

do {
foreach ( (array) current($wp_filter[$tag]) as $the_ )
if ( !is_null($the_[‘function’]) )
call_user_func_array($the_[‘function’], array_slice($args, 0, (int) $the_[‘accepted_args’]));

} while ( next($wp_filter[$tag]) !== false );

array_pop($wp_current_filter);
}

I am at a standstill with my site down. please help me get this sorted out.
Thanks in advance