Problems with AS1 to AS2 - type mismatch

hi …

i have a problem running this script under AS2 (flash player 7) … with AS1 (flash player 6) there is no problem. Only AS2 cause an error …

Type mismatch.
var dX = parseInt(_root._xmouse - this.rotateTarget._x);

i have no idea what part of this line is not good enough for AS2

could I ask for help or advice? thanks