Jeez, for a minute I thought my brain really had crashed - I found an ad for the preview of Capricorn One the week before it came out on June 2, 1978 (NOT 1977 as the imdb would have it - they put December of 1977 as its release date and say it came out in Japan - well, really? Not a Japanese film and I doubt it was even finished by then). And yes, while they didn't have the title in the almost full page preview ad, they did have the graphic and ad line. And it was at the National. How could I be that off? But then I went back to April, two months before the release and voila - preview at the Village. The same kind of ad but no graphic - just the ad line. So, whew, and glad my memory is still mostly working. Interestingly, both previews were in 70mm.
So the Capricorn preview was at the National? My memory has me seeing it at the Bruin. Is that where it played? If not, that part of my own brain crashed long ago.
I still have no idea why I didn't go to see Parallax. Though it's not impossible that I did. When I watched it years later, a few scenes did seem familiar.