Unfortunately the code you posted produces the same results in Ie6,7 and Firefox so it's hard to guess what the problem may be as there is probably another trigger in code not shown.
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
padding:0px 8px 8px 4px;
As Ryan said the widthless Sidebar will not be a lot of use as fluid content will eventually push it to 100% wide.
IE6 and 7 don't understand "inherit" and indeed you would not want the height inherrited into that element anyway as that would limit the element to a fixed height (should it be able to reconcile it's height from a fixed height parent of course.)
Have you got a link to the problem so we can debug further?