warning: array_keys() [function.array-keys]

In my Drupal 5.12 install I'm receiving the following errors on the /user page after visiting "Create new account" tab (/user/register) and submitting a user name and email address:

* warning: array_keys() [function.array-keys]: The first argument should be an array in /home/public_html/sites/all/modules/workflow_ng/states/states.module on line 270.
* warning: array_intersect() [function.array-intersect]: Argument #1 is not an array in /home/public_html/sites/all/modules/workflow_ng/states/states.module on line 270.
* warning: array_keys() [function.array-keys]: The first argument should be an array in /home/public_html/sites/all/modules/workflow_ng/states/states.module on line 270.
* warning: array_intersect() [function.array-intersect]: Argument #1 is not an array in /home/public_html/sites/all/modules/workflow_ng/states/states.module on line 270.
* warning: array_keys() [function.array-keys]: The first argument should be an array in /home/public_html/sites/all/modules/workflow_ng/states/states.module on line 270.
* warning: array_intersect() [function.array-intersect]: Argument #1 is not an array in /home/public_html/sites/all/modules/workflow_ng/states/states.module on line 270.
* warning: array_keys() [function.array-keys]: The first argument should be an array in /home/public_html/sites/all/modules/workflow_ng/states/states.module on line 270.
* warning: array_intersect() [function.array-intersect]: Argument #1 is not an array in /home/public_html/sites/all/modules/workflow_ng/states/states.module on line 270.

* Your password and further instructions have been sent to your e-mail address.
* You must login before you can proceed to checkout.
* If you do not have an account, you can click here to create one.

Anyone have an idea what might be causing this?

thanks!