At the application which I work on , there are main tab panels. When I click one of them , it gives me a script error. The detail of the script is , Invalid argument Line 7422 setLeftTop. (ext-all-debug). By the way, when other panels are clicked, there is no error like this.

setLeftTop : function(left, top){
var me = this,
style = me.dom.style;
style.left = me.addUnits(left);
style.top = me.addUnits(top);
return me;

setLeftTop method is invoked in setPosition method. When I look at debug mode, at one of the invoked setLeftTopMethod, both parameters are NaN. Because of that, It gives the error "Invalid Argument". I could not resolve this situation.
What can cause this situation ?

Thanks for the replies in advance..