Using customvalidator, button click event won't fire until 2nd click

Basically, I have a button that should submit the page if the textbox isn't empty.  If it IS empty, the customvalidator text appears.  However, if the customvalidator text is there/activated (which means that the textbox was empty and I clicked the button), and I fill in the textbox, I need to click the button twice to submit the form - once to clear the customvalidator text, and the second time submits the form.  Why is this?  Is this expected or am I doing something wrong?
More details:

I have a customvalidator associated with a textbox, and have set the ClientValidationFunction to some javascript in the master page.  The reason I do this is because I change the text of the button within the javascript if certain requirements are met.  Is this somehow blocking the button click event from firing that first time?

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