Código PHP:
SELECT c.comment, c.date, c.ID_COMMENT, c.ID_MEMBER AS ID_COMENTADOR, m1.memberName AS nombrecomentador, m2.avatar as imagenuser,c.COMMENT_MEMBER_ID AS ID_MURO_USUARIO, m2.memberName AS nombremuro
FROM (smf_profile_comments AS c, smf_members AS m1, smf_members AS m2)
WHERE c.ID_MEMBER = m1.ID_MEMBER
AND c.COMMENT_MEMBER_ID = m2.ID_MEMBER
ORDER BY c.ID_COMMENT DESC
Bueno al verlo a simple vista y con mi escaso tiempo te dire que en la consulta que haces de seguro que te corre en tu manejador de mysql, pero creo que en php no lo hara elimina el "c." en "c.comment, c.date,etc" talvez este el problema ahi