  We generalise the RS braneworld model by taking into account a general
stringy bulk containing the scalar dilaton field and the two-form Kalb-Ramond
field, apart from gravity. Assuming small fluctuations around a RS background,
the back-reacted warp factor is obtained. It is shown that the fine tuning
problem in connection with the Higgs mass reappears in a new guise and the
effective modular potential fails to stabilise the braneworld.
