City Screen: Worked vs. non-worked tiles.

Don't know if it's a hardware/graphics problem or not...

I thought in the early game it was cool, but mid-game I am noticing this. On a city screen, I'm only seeing the yield for the tiles I'm working, and maybe 1-2 others. I can't other tile yields, nor can I tell if any tiles are being worked by near-by cities. If I remove a citizen, and choose a 'in-the-dak' tile, the yield will be displayed, but not worked. Clicking again, will work the tile.

Anyone experience this?

I believe the double-clicking behavior is intentional; if a yield is blacked out but within the city radius, it means a nearby city's already using it. Clicking once frees that tile for use in the city you've selected; clicking again actually works it.