Registration pop-up missing it's sign up check boxes

Hi guys,

I am an admin on a site that uses constant contact. We have 2 newsletters that people can sign up to by checking the registration pop-up boxes. For some time though those check boxes have been replaced by the text "null" (see the attached image). People can still register on the site but they can't get in the lists that allows them to receive the newsletters.

I can revert the site to a previous state that will get the registration back but this is the second time that this has happened and would like to have it fixed in another manner.

Is there a patch that can solve this? Am I a overlooking something that might cause this?

Thank you for anything that can help me resolve it.