Normally when that is grayed out it indicates not all of the mandatory fields are completed or there is some conflict with an existing name. If you could provide a screenshot of the window with the button grayed out that would help.
What James said +1.
Also there could be a message at the top of the screen indicating the missing field or why you're not allowed to "submit". Verify there's no message at the top of the dialog window.
But a screenshot would be a big help.