Strange error Help! :)

I created a site using New Blog Template and the site is giving this error …

Warning: array_key_exists() [function.array-key-exists]: The second argument should be either an array or an object in /home/nueranet/public_html/myxocolatllife/wp-includes/widgets.php on line 858

On the main site there are no errors but as soon as I make a new sub site which is part of the network.

Any ideas regarding this error would be most welcomed.