Scripting error resulting from permissions?

I've created a pageInit script that executes upon creation of a new sales order. The script checks the customer record to see if there is a reminder message, if there is it displays that message as an alert.

My script works fine under my admin role but when I test it out as a sales person I get this error.

I've checked the rights on my custom entity field and they are available to view by everyone. Any ideas on what to try?

Thanks!

 function pageInit(type) {   if (type != "edit")    {     customer_id = nlapiGetFieldValue('entity');        var soalertmsg = nlapiLookupField('customer',customer_id,'custentity43');        if (soalertmsg != "")       {          alert (soalertmsg);       }    }  }