When you look at the source code, can you identify the banner code & if so, does it look like the "fresh" code from x10hosting?
Not used NVU for a while, but I think when I did, what discouraged me from using it further then was its messing up php code by rearranging it, etc, rendering it useless. I dont know whether that is always the case or I had not just found out how to stop that.
I am using the corporate plan ad code ... Currently, even if the code is there, it's not showing - ie. the ad space is blank, but I think that is a temporary problem from x10hosting as I have not changed anything on my site & it was working before.
You could instead of using the NVU editor just try out another OR simply do it via the CPANEL file manager and add the code from there.