Problem with IE 7 and CSS button background

I have a contact form on my page, and I used css to change the submit button to an image. In most browsers this works fine, the image displays and the text is pushed off screen with text-indent. In IE 7 there appear to be two issues:
1. 'submit' text still appears
2. The background image is being cut off.

Does anyone know how I can fix these issues?

thanks

page: http://mainst-group.com/index.php?option=com_aicontactsafe&view=message&layout=message&pf=1&Itemid=73

code:

<input type="submit" id="aiContactSafeSendButton" value="Send" style="float:left; margin:2px;">

width: 97px;
height: 77px;
border: 0;
background: transparent url(../../../images/send-button.jpg) no-repeat center top;
text-indent: 1000em;
cursor: pointer;
cursor: hand;