i think i had it before.
if i'm not mistaken, you haven't develop the technology necessary to build on arid tiles, that's why your arid tile is highlighted (well... barely) in yellow instead of green.
When you try to build something, i think the game goes with something along the lines: "is the selected tile available for building? yes => build, no => select the first next available tile and build on it"
In galciv2 it didn't happened because the list of available buildings was filtered according to the selected tile, ie on a tile needing terraforming, you could only see the terraforming "building".
Hope this help!