As the matter is fixed, there was not any problem. But we can't say there won't be in the future.
The main thing to remember here is a program called "YieldBuild". I guess YieldBuild is owned by the CEO of HP. What Yield Build does is, optimizes the ad locations for maximum conversion. If it thinks AdSense will convert more than the CPM HubPages ads, then it won't show any HP ads. So you may not get any HP ads impressions. If it thinks HP ads will convert more than AdSense, it will show only HP ads (excluding the big 300*250 ad block within the hub).
You can know more about YieldBuild at yieldbuild.com