Ok,sometimes Maya won't let you use the split poly tool on some faces. Go to the split poly options and turn off snapping. It should work now. You may have to make sure your vertexes are merged. Afterwards, turn snapping back on.
"The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man."
George Bernard Shaw - Man and Superman