I've stripped out most of the unnecessary stuff and placed the needed files at the following location
http://www.global-plus.co.uk/menuTest/index.php
As you can see it works fine in IE (apart from the alignment which I messed up when removing stuff) but doesn't work in FF.
The html code is generated in the following PHP function.
[PHP]
function menu() {
print"<li><a href='tribe_main.php'>HOME</a></li>";
print"<li><a href='tribe_vcs.php'>VCS</a></li>";
print"<ul>";
print"<li><a href='tribe_vcs.php'>SEARCH</a></li>";
print"<li><a href='tribe_vcs_add.php'>ADD CLAIM</a></li>";
print"<li><a href='tribe_vcs_my.php'>MY CLAIMS</a></li>";
print"<li><a href='tribe_vcs_player_claim.php'>MASS CLAIMS</a></li>";
print"<li><a href='tribe_vcs_mass.php'>MASS LOGIN</a></li>";
print"</ul>";
print"<li><a href='tribe_stats.php'>STATISTICS</a></li>";
print"<ul>";
print"<li><a href='tribe_stats.php'>TOTALS</a></li>";
print"<li><a href='tribe_stats2.php'>AVERAGES</a></li>";
print"<li><a href='tribe_stats3.php'>CAPTURES</a></li>";
print"<li><a href='tribe_stats4.php'>LOSSES</a></li>";
print"</ul>";
print"<li><a href='tribe_attack.php'>ATTACK TIMER</a></li>";
print"<li><a href='tribe_player_pos.php'>VILLAGE LISTS</a></li>";
print"<li><a href='tribe_mailing_list.php'>MAILING LIST</a></li>";
print"<ul>";
print"<li><a href='tribe_mailing_list.php'>TRIBE MAIL</a></li>";
print"<li><a href='tribe_mail_cl.php'>CL MAIL</a></li>";
print"</ul>";
print"<li><a href='tribe_hc.php'>HIGH COUNCIL</a></li>";
print"<ul>";
print"<li><a href='tribe_hc.php'>CL LISTS</a></li>";
print"<li><a href='tribe_hc_change.php'>CHANGE CL'S</a></li>";
print"</ul>";
}
[/PHP]