Custom controls not working with Datapager

Hi,
In order to get around the ImageButton problem with IE10 i have had to create a custom control (ImageButtonIE10) that inherits from ImageButton with a class placed in the app code folder. The control is used on a page with a ListView and Datapager and when the page first loads it all functions as expected with the new imagebuttons all working as expected, however, as soon as i click the datapagers next button the page crashes. I know it's to do with the custon control because of the error message and because if i change the page back to normal ImageButtons everything works again (except you can't use it in IE10).
Here's the error message...
Message Object reference not set to an instance of an object. StackTrace at NewWebControls.ImageButtonIE10.LoadPostData(String postDataKey, NameValueCollection postCollection) at System.Web.UI.WebControls.ImageButton.System.Web.UI.IPostBackDataHandler.LoadPostData( ...