I keep getting an error when importing to update the class on line items on a sales order. The error reads "Please Enter Value for Amount" when I try to update class on some sales orders. I am not updating rate, qty, price level, or amount. These sales order items already have an amount filled in. Anyone else experience this issue?

Are you checking the Replace sublists option? I wouldn't use that in your scenario, but I could see that error message happening if you are. That basically wipes out all existing line items and adds whatever is in your import file, so if you have that box checked, the error message would make sense. You'd be basically trying to add a line with only Class filled in.