The xpad USB linux kernel driver incorrectly identifies
a certain dance pad as not being a ddr pad.
To fix:
Replace this line in drivers/usb/input/xpad-core.c:
{ 0x0c12, 0x8809, 0, "Level Six Xbox DDR Dancepad" },
with this:
{ 0x0c12, 0x8809, 1, "Level Six Xbox DDR Dancepad" },
-Dom
(P.S. dance pad support is going to be in the
mainstream linux kernel starting v2.6.19)