text in layers-inconsistent link underlines on PC

I need labels on my main navbar that are two closely spaced lines of text.
I've done it by putting the text in a layer and adjusting the layer width so
that my text wraps the way I want it to. As text alone it looks fine on both
Mac and PC.

I also want the text to be underlined on rollover, and I've used the
following CSS in my style sheet to accomplish that:

a:link {
text-decoration: none;
}
a:hover {
text-decoration: underline;
}
a:active {
text-decoration: underline;

This works great on my Mac in Explorer, Netscape, and Safari. But in Explorer
on a PC, the underlines are inconsistent: some underline both lines, some just
the top line, and some single text is underlined and some is not. Nesting/not
and wide vs. narrow layer width don't seem to fix the problem. What's up? How
can I make the underlines work consistently on PCs?

Thanks!
Cindy