border-bottom not working in IE 7?

[Errrwin]

I'm working on a really simple template which has (amongst other stuff :P) the following css:

#navigation a, a:visited, a:link, a:active {
	font-family: Verdana, Arial, Helvetica, sans-serif;
	text-decoration: none;
	font-variant: small-caps;
	text-transform: lowercase;
	font-size: 12px;	
	color: black;
	border-bottom: 1px solid white;
}

#navigation a:hover {
	border-bottom: 1px solid #FFA500;
	font-variant: small-caps;
	text-transform: lowercase;
	font-size: 12px;
}

To get a neat little orange line appear when hovering over a link in the navigation div.

Firefox likes it, IE does not.

Is this something I'll have to live with "as it's IE" or am I screwing up something in my coding?

[EcoSee]

add:

text-decoration: underline;

to the hover section such as:

#navigation a:hover {
border-bottom: 1px solid #FFA500;
text-decoration: underline;
font-variant: small-caps;
text-transform: lowercase;
font-size: 12px;
}

[Errrwin]

That gets me a nice black line underneath the hovered-over link, but I want an orange one!