Is the P3.3 level at a constant 2.3 V level when you keep the pushbutton pressed?. Are you sure there is not a square waveform at that pin?.
A sound P3.3 pin should be externally driven to '0' level without problems, no matter whether your code writes '0' or '1' to that pin. Except for the case your code is writing 1s all the time or 1s and 0s alternatively. This is due to the strong pull-up that exists only for a short time whenever the pin is set to '1' (for example using setb P3.3).

Alfredo.