Forms Check Box not working

We have several forms that we have available to our users. On the forms are "Check Boxes". The users fill out the forms and then email them to a particular mailbox. Whenever a particular user tries to fill out the forms the checkmarks disappear from the boxes when he emails the forms. If he saves the completed form to his hard drive first and then emails it, the check marks are in place, but if he tries to email the form while IN the form the marks are not visable to the person receiving the email. Any ideas??

Thanks for you help.