We've seen cases where the scroll bars in the Grade Center weren't showing in IE 8, so those using IE 8 may want to try using Firefox instead. This bug will be fixed in the next Service Pack (SP5) update.
You might want to suggest that your students use a different browser anytime they're having problems with Blackboard as the first possible solution. This very often fixes problems. Here is a list of the most compatible browsers for Blackboard that you can give your students.