Post your code or something that shows what you have attempted. Try using the click and also the press and release options. These options do the same thing, so you could be sending the wrong mouse button ID.
The modifications would only affect what Arduino files are included ( WProgram.h changed to Arduino.h ), not the actual operation of the class.
This will though:
void Mouse_::click(uint8_t b)
_buttons = b;
_buttons = 0;
The move sends the x,y, and current button, so that function effectively does nothing but set _buttons to '0'
Try replacing the x,y params of move to the last known position ( or where you want the click ).