Need help: Stratix II GX Audio-Video board and LVDS inputs

I am trying to use a Stratix II GX Audio-Video development board and have

been able to get LVDS output going ok.

However, when I try to use alt_inbuf to get the LVDS input as in:

hsm2: alt_inbuf

port map(

i => hsm_rx_d_p(2),

o => my_input));

I get the error message from Quartus II that O is not connected.

Any thoughts/ideas?