Not sure but you might try replacing this
Code:
.centerColumn {
padding: 1.8em;
border: 5px solid #633;
margin:1em;
}
with this
Code:
#indexCategories {
z-index: 500
padding: 1.8em;
border: 5px solid #633;
margin:1em;
}
Also the quotes are not necessary but seem to be functioning here
Code:
#mainWrapper {
text-align: left;
width: 795px;
vertical-align: top;
background: #fdfde9 url("../images/backgroundfull.gif");
border:5px solid #333;
margin:1.5em;
}
I do not see a specific reason for the IE glitch but am theorizing that it may be your background image??? and why using z-index might repair as this should bring this to the top
As a test you might comment out the backgroung image and see if this alters the issue or if it still remains
BTW: Nice job on the template....very clean and classy!!