Ah ha! The center part of the 2000 join should be:

FROM HISAppt.dbo.sysUsers u

LEFT JOIN (HISAppt.dbo.sysMembers m

JOIN HISAppt.dbo.sysUsers r

ON m.groupuid = r.uid) -- groupuid not memberuid

ON m.memberuid = u.uid

LEFT JOIN dbo.sysLogins l

ON u.sid = l.sid

That fixes the group thing.