What options do you use for the password protection?
There are two ways you can make a form unfillable: With password protection that specifically prevents form filling, and by flattening the form. Chances are you've had a solution installed that was flattening your forms before they were mailed out. Without knowing your existing solution, it's impossible to say what's wrong. You can download and install a free form flattening tool from here: Free Acrobat Automation Tools
You may want to still look into password protecting your documents. To prevent form filling, make sure that you set "Changes Allowed" to "None" on the security dialog:
Thank you both very much. When we password protect and send, it's still fillable.... off to try that flattening tool. Thank you so much! I will let you know.