Hardware Secrets posted a quick guide about fixing the IE8 Black Bar Bug
>> Fixing the IE8 Black Bar Bug
After migrating to Internet Explorer 8 on Windows XP, the menu and the favorites bar would go black with no apparent reason. So far we didn't discover why this happens and when or if Microsoft will release an update to fix this bug. Meanwhile, learn the trick we are using to restore the menu and the favorites bar to its correct color. The problem can be seen on Figure 1.
>> Fixing the IE8 Black Bar Bug