Steps to reproduce:
1. Deploy "web-form-portlet-188.8.131.52.war" and start Liferay 5.2 SP4
2. Place Web Form portlet on a page
3. Go to the portlet's configuration
4. Switch to "Form Fields" tab
5. Add a new field and set its type to "checkbox"
6. Go back to your page and fill out the form, but do not set anything for the checkbox
7. Send the form, you will get an error message: "You have entered invalid data. Please try again."
8. Fill out the checkbox as well, and attempt to send the form again
Result: Although you will get the success message, the previously displayed error message is still present