Weird appearance of page menu bar in IE8

It looks fine in Firefox and Chrome, but the horizontal page menu bar on http://theagnonschool.org is too fat in IE (see attachments).

I'm using WordPress 2.9.2 & Atahualpa 3.4.3.

In addition to what I've specified on ATA's Page Menu tab, I've styled the menu in Add HTML/CSS Inserts this way:

/*color drop down menu*/
div#menu1 {
background: #1D3A7B;
border: solid;}
div#menu1 ul.rMenu li a:active {font-weight: bold;}


Any ideas on what may be going wrong in IE?
Thanks
Lila