I had this same issue, the way I ended up fixing it was by changing the following in Oxygen.css (or equivalent)
changed this:
.brd .item-summary .subject-title {
padding-left: 1.417em;
}
.brd .item-summary .info-topics,
.brd .item-summary .info-replies {
margin-left: 100%;
text-align: center;
width: 7em;
left: 965em;
}
.brd .item-summary .info-forum {
margin-left: 100%;
text-align: center;
width: 20em;
left: 952em;
}
.brd .item-summary .info-posts,
.brd .item-summary .info-views {
margin-left: 100%;
text-align: center;
width: 7em;
left: 972em;
}
.brd .item-summary .info-lastpost {
margin-left: 100%;
left: 980em;
}
.brd p.forum-noview .info-replies {
left: 972em;
}
to this:
.brd .item-summary .subject-title {
margin-left: 20px;
}
.brd .item-summary .info-topics,
.brd .item-summary .info-replies {
text-align: center;
margin-left: 380px;
}
.brd .item-summary .info-forum {
margin-left: 100%;
text-align: center;
width: 20em;
left: 952em;
}
.brd .item-summary .info-posts,
.brd .item-summary .info-views {
margin-left: 470px;
text-align: center;
}
.brd .item-summary .info-lastpost {
margin-left: 540px;
}
.brd p.forum-noview .info-replies {
margin-left: 460px;
}
You'll need to tweak the numbers until you get everything positioned properly in Firefox, then in your Oxygen_ie7.css you may need to make some additional tweaks to get it to look right, though for me I don't think it was necesarry. (Tried initially just tweaking in the ie7 css, but the margin-left was set to 100% so it wouldn't let me I suppose, maybe there was a better way to do it, but it worked)