I was also getting the same message, I just installed Face Time a few minutes ago. All I did was follow these instructions that I found and it worked.
1) Visit My Apple ID at https://appleid.apple.com/.
2) Log in with your other Apple ID and password.
3) Select the Manage your account link.
4) Choose Name, ID, and Email Address from the left side of the page.
5) Next to Primary Email Address, select Edit so that you can change the email address associated with this Apple ID.
6) Once you've made the desired change, select Save Changes.
7) Choose Sign Out from the top right of the page.
If you would like to have the verification email resent to you, please sign intohttps://appleid.apple.com/ with the Apple ID you want to verify, and make sure there is not a typo in your Primary Email Address. Select the "Edit" link to the right of your email address to make corrections and then click the "Save Changes" button. Once the typo is fixed, or if there is no typo, click the "Resend" link under your email address.
Basicaly you are reverifying your ID, I did not have to change anything.