Visual Basic.Net and Posting Forms aspx

I have used visual basic.net (beta 2) to create a form, added some client side validators and some buttons (both server side and HTML). The form and validation controls appear to work fins fine, however, the form is not posted back to the server when I click a button (only the validation occurs). I have tried changing lots of things without success and need some help. What I want is when the user clicks the button, the form is validated and if OK posted back to the server.

For more information, I tried changing one of the drop down lists to autoPostBack and the form is posted when I change the contents of the list. I guess the form is OK, some problem with how I am using the buttons.

Thanks for any help.