I have experienced a couple of "build queue" issues, where after completion of a construction it was impossible to select what to build next in a city. Until recently I had no clear idea why this happens, and a reload cured the problem (as was suggested in these forums). Although I can confirm that I am in the process of razing/annexing foreign cities but can*t really pinpoint the exact cause on this.
Today I noticed a link to the buying of city tiles function, as the both functions fail simultaneously in my current game. A reload still fixes the problem, however the buying of city tiles seems to "crash" the game in a reproducible way: I can sometimes purchase one tile, but after that the button is grayed out and also the build queue "freezes" and cannot be changed (any kind of construction unit: building, wonder cannot be selected).
Civ 5: 1.01.705
NiGHTS v12.0
Update: I went back and forth with this and it turned out that once I had viewed any puppet city (where obviously no changes to build queue can be made or tiles be bought) and would then view any of my own cities in the same or even subsequent turns, the actions were not allowed there either. If I take the exact same savegame and go directly to view my own city, both the tile purchasing and build queue work as they should. I hope this helps in narrowing down the problem and eventually to solve to it.
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