Flex: Error when I add decimals

Question

When I put some value (123 for example) the numberValidator work well. When I put "123." works fine too.

But when I put 123.0 (or any number) the text NULL appear, as an error message. What I have wrong?

This is my validator:

var validator:NumberValidator = new NumberValidator();
     validator.allowNegative = false;
     validator.required = false;
     validator.minValue=0;
     validator.decimalSeparator=".";
     validator.thousandsSeparator=",";
     validator.property="text";