ASP.NET Validator needs two clicks to fire

[Remy]

Hey
I have a textbox where the user needs to enter a number and a submit
button.
Attached are two validators (RequiredFieldValidator and
RangeValidator).
Now if the user does not enter a number and presses submit, the
validator fires and the user gets the error message as expected. But
now, if he enters the number, he needs to press submit twice.
After the first click, the error message disappears, but the form is
not yet submitted.

Am I doing something wrong or whats a good workaround?

Cheers

Remy