Problem - Summary Validation, need to submit twice to fire

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I'm having trouble working with a Summary Validation control. I need to
click my submit button twice for the Summary to display when validation
errors occur on the page.

Background:
My page contains a radio control which the user must answer to finish the
page entry. If user hits submit button without selecting item from control,
summary validation error displays. In this case one click is sufficient.
Once the user selects choice on control, the page dynamically enables
controls below, containing various textboxes and calculation buttons. For
example there are four controls which are validated. If I hit submit without
entering anything the validation summary fires correctly after one click of
the button. If I enter data in the first two controls correctly and hit
submit, nothing happens. If I click submit again, the validation summary
fires correctly indicating that the final two textbox controls require entry.

Any ideas why I need to click twice.

I am using Validation Groups, since there is another inner calculation
button which only checks the entry of the first two textbox controls.
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Thank-you,
Barbara Alderton