Take a look at this in ie 6 and 7 and you will see the services drop down (jquery plugin) does not allow you to scroll down further that the second option. Its clashing somewhere with the quote box underneth. Works fine in firefox.. obviously! lol
I don’t have access to ie right now but just looking at your css in firebug I see that you have the z-index for #second_head_right h1 lower than #nav_wrap which will put it behind.
I would just set the z-index for #nav_wrap to 2 and the z-index for #second_header to 1 (don’t forget to give it a position of relative).