<BODY><P>Yuvan replaces Dhina</P> <P>Silambarasan is currently working hard on <EM>Silambattam</EM>. And why not? After the lukewarm response to his <EM>Vallavan</EM>, the young actor was banking on <EM>Kaalai</EM> to succeed. However, <EM>Kaalai</EM>