Submt variable not set in IE

I have a form which seems to work fine in Firefox but not so fine in IE6/7.

The form submits, via the POST method to itself. When I reload the page I check to see using the following code:

         if ( $_POST['Submit'] == 'submit' ) {

Lower down the page I have the submit button defined as follows:

        <input name="Submit" type="submit" src="images/savebtn.jpg" value="submit">

Originally I had the type set to image (hence the src attribute) but have just changed it to a submit type to see if it works better - as i say, it doesn't,

Before the button I have the form defined as ...

          <form name="budget" method="post" action="mybudget.php">

I am using PHPED to write this code and when I run it with the debugger and look at the variables, the $_POST['Submit'] variable isn't there. There is, however, a $_POST['Submit.x'] and $_POST['Submit.y'] variable.

Any idea why this isn't working.

Website is at www.jwedding.co.uk

Thanks
M