Thanks CheleA. I took a Google look at 40 Casa and it does appear to look like it was built by the same people. It reminds me a lot more of Mesa Verde in layout though. It is sad that we may not have an opportunity to visit in some time.
Unfortunately, you are correct. That area in particular is very unstable. I had the chance to visit several years ago and it was impressive. I was told the sites are indeed related. The funny thing is how they were named. "40 Casas" means "40 houses", whoever came to it, said "that looks like 40 houses" and the name stuck -- I think it's 33 houses.