openocd does not discover JTAG device

I have three Olimex prototype boards: two lpc2106 and one lpc2148. They have all worked with my Olimex OpenOCD JTAG device in the past, but now only one works–a lpc2106. All three boards successfully run their programs in standalone, non JTAG, mode.

I have verified the jumpers on the boards.

What is it that I could have done to cause the JTAG port to not work?

Thanks,