I was not able to test your page because i don't have all the includes, but i did see that you made the change correctly, however i just want to mention that you only needed to make this change on the Date of Birth field, you did not need to make it on all the other fields.
I did another test with my own form (using the contact from in Form Builder) and i did see the issue and changing the onblur to onfocus did resolve the issue for me and i tested with IE 7.
Try clearing your cache of your browser and see if that resolve the issue.