Is this an iOS application? If so, there is a bug with the scrolling of native text controls. The following should fix it:
<fx:Style>
@namespace s "library://ns.adobe.com/flex/spark";
@namespace mx "library://ns.adobe.com/flex/mx";
@namespace local "*";
s|TextInput {
skinClass: ClassReference("spark.skins.mobile.TextInputSkin");
}
s|TextArea {
skinClass: ClassReference("spark.skins.mobile.TextAreaSkin");
}
</fx:Style>