The plot thickens, I can no longer specify a birthday for a newly created contact, the field is not displayed at all. You can try this yourselves, I believe this is a Gingerbread/Motorola bug. I have exported all my contacts as a vcard and the birthdays are definitely there - they are just not displayed under 'Contacts' nor are you able to set a birthday for a new contact....

I cannot log a call to AT&T due to me living outside US, but you guys can do it...