Doesn't seem to be super well documented, so I figured I'd regurgitate it here.
In Firefox, apparently whitespace in a table is treated as "important" by default, and prevents wrapping. To turn this off add this little CSS nugget
<style type="text/css">
{
white-space:normal !important;
}
</style>
Source:
http://www.telerik.com/community/forums/thread/b311D-ehhed.aspx