For what it's worth, I've had trouble with plain, white, featureless elements. Perhaps your pillars are like that. If there are no features on the surface for Photoscan to recognize, then it's possible that it won't be able to model it. Because it can't get a grip on the depth information it doesn't know what it's looking at.
If you can, you might want to make those pillars more recognizable by putting some distinct marks on them. You can always paint those marks out in Photoshop when you generate your final texture. But you'd probably have to make sure you can get them off the pillars themselves too...
Hope this helps.
Jon