Required select fields get error message "This field is required!"

Okay... Your suggestions made logical sense, and I've gone through and disabled every plugin, and found nothing that resolves this. There were no fatal errors. I even took the step of asking the hosting company to move the site to a newer server. They have turned off Mod Security. I'm stumped...

Please PM backend super administrator login credentials and will take a look.

The fields failing specifically are select types. You have them configured within invalid values. For example the below.

{lang en}Male{/lang}{lang es}Varón{/lang}

That will not validate in CB once it does its post cleaning. You need to supply a language string and translate it in CB using CB language plugins as that usage will not work properly for validation.