This morning after conquering the lower-right sector I seem to only be able to queue up two buildings. I can add a third, but within 10 seconds it will be removed. I've tried reloading multiple times and the issue persists, so it doesn't seem to be an issue with local corruption.

Also: occasionally after trying to unsuccessfully add a third item it will get stuck at the point where I can't even add a third item. Even with two items in the queue all buildings will be greyed out with the "Your build queue is full" error message.

Wow... in further testing while I was trying to submit this I now have a 4-item queue. One of the buildings on my queue no longer is shown, but the plot of land where it is to be constructed still exists and hasn't been removed after over a minute. Reloading my client removes the 4th item, but the 1st or 2nd still does not show up (sorry, they are the same building). I don't have the resources currently to see what happens after a building is completed. Three refreshes later and I still see 2 items in the queue, but actually show plots for 3 and can add a 4th temporarily.