I used ic-atheme for sometime until changing templates few days ago. Nice template, just wanted to try something else.
As I recall, try includes/css/stylesheet_header_menu to increase the width of the top cat nav, try both places where default below says "750px" (don't know how to put in red font):
div#dropMenu {
width:750px;
margin:0 auto;
text-align:center;
z-index:1000;
position:relative;
}
div#dropMenu ul {
margin: 0;
padding: 0;
}
div#dropMenu li {
position: relative;
list-style: none;
float: left;
line-height: 1em;
}
div#dropMenu ul.level1 {
width:750px;
margin:0 auto;
text-align:center;
background:#F2F2F5;
height:25px;
z-index:1000;
}
You have very long category names, which will take up any available width. Note that at some point it will wrap to a second line, depending upon customer's monitor/resolution. The second line will not look pretty in IE7, as it will drop down in to the blue search bar area.
I was about to re-arrange my category layout to make sure it never went past one line; until I decided to try another template.
Hope this helps.
SPH
https://www.prommart.com - zencartzen template
https://www.fashion-mart.biz - zencartzen template (under development)
https://www.prom-mart.com - test site, testing mystic river template
Have a couple other domains under development still with ic-atheme template.