Commented Issue: Combobox button not displaying in IE7. [25271]

The button on the combobox control is not displaying on page load in IE7. Then on postbacks the button alternately displays and disappears. Any ideas why this is happening? I've tried to reproduce this in a simple web site where there is just a textbox, button(to cause the postback), label and combobox controls and i have been unable to reproduce this behavior.

Any ideas about why this is occuring would be helpful.

Also the comboboxes are included in an ajax update panel if that makes any difference.

css being used:
.ajax__combobox_textboxcontainer input
{
background-color: #fff;
border: solid 1px #B7B7B7;
border-right: 0px none;
color:#666;
height:15px;
}
.ajax__combobox_buttoncontainer button
{
border: solid 1px #B7B7B7;
}
Comments: I get the same issue with IE7, does not happen all the time, usually on initial load. The button container is correctly in place, the button just is not there when bug occurs. My Combo Boxes are also in Update Panels. It seems to be only happening when the rendering of the page takes over 5-10 seconds (hence initial load for me), when it loads quickly it does not seem to have the issue. This is why I think it can not be reproduced with simplified version. Maybe build a deliberate load time delay into code to see if that causes the bug to appear.