Dialog scrolling problem in IE6 and IE7

Dialog scrolling problem in IE6 and IE7

Hi guys,
I am using a dialog where my content causes scrollbars to appear. In IE8 everything acts as expected and scrolls smoothly. It's only using IE6 and IE7 that causes the problems. Content doesn't scroll at all. Scrollbars move, but content doesn't and then suddenly it does, but appears on top of the titlebar.

Any ideas?

thanks in advance

Tony