Sigh...IE can't read it, but neither can FF 2.0.
I thought it was working fine because I refreshed the page in IE6, IE7 and FF 2.0 and it looked perfect in all three, but it turned out that FF was still going from the cached CSS that worked fine previously.
Anyway, I got around it all using a conditional:
<link rel="stylesheet" type="text/css" href="style.css" />
<link rel="stylesheet" type="text/css" href="style_ie.css" />
And just separated the IE/FF styles into their own files. It's more work when/if changes need to happen, but it's better this way in the long run I s'pose.
And it works.