I created a ticket for this issue, and it has been closed as "expected behaviour" with this comment:
So, clearly, this isn't a Cool VL Viewer bug.
When I tested in Firestorm, which I rarely use, the buildings continued to rezz correctly, until I flushed my cache, when (as I expected), the buildings all turned into apples. Which suggests the server fix is blocking the loading of the sculpt maps of these "corrupt" objects. Intriguing...