Since this issue is regarding your Microsoft Account you may need to adjust your settings in your connected services in regards to Facebook and Twitter.
- Sign in with your Microsoft Account ( Windows Live) ID at http://profile.live.com/Services.
- View the connected services you use to Microsoft Account, select Manage your accounts.
- Select Facebook or Twitter. Follow the prompts to connect your accounts together.
- Then try enabling Facebook in the account settings on your phone, select Start > Settings > email+accounts.