。
He might say something vague again.
Literal
He [topic-は] again vague thing [object-を] say might.
曖昧な事を言う ('to say vague things') uses 曖昧 (あいまい, 'ambiguous, vague'). かも知れない is the full spelling of かもしれない ('might'). また ('again') suggests this is a recurring frustration. The sentence expresses resigned anticipation of someone's habitual evasiveness.