Command M3 doen´t work properly

Hi every one..
I have a problem since this morning on my cnc router. right now does NOT respond to the M3 command.
when I use the "push buttom" in graphical interface, everything is fine, but it doesn't respond to the line command send.
All other M5, M7, M8, M9, M1 commands works OK.
I notice that the M3 works in "reverse" (¿?) if I turn on the spindle engine through the graphical interface, when I send the M3 command, it "turns the spindle motor to off" (¿?) Just like M5 does. So I have two ways to cut off the motor, M3 and M5
Can someone give me a hand with this issue?
Thanks in advance... Marfil

Thanks a lot, next week I Try it.

Finally your're right. It was the solution.
Thanks a Lot.
Marfil