Version 0.5.7567 on Win7-64 bit
Found the following in a single player skirmish:
I paused the game and implemented a number of building orders. This totaled about 15, and each generated a thumbnail image of the building under development. Each of these 15 thumbnails was placed in a row across the screen, such that the last few overlapped the game control UI in the top-right corner. Even though I could see the game speed controls underneath / between the thumbnails, the buttons were not responsive when I clicked them. In fact, the game was stuck in pause until I looked up hotkey commands for game speed and was able to resume play.
Observed: game speed and other UI controls unavailable with sufficient number of buildings in production
Expected: game speed and other UI always accessible
Please let me know if any additional information is needed.