Sounds like a connectivity problem. Sounds like you're losing connection to the server when your city is idle for a few hours as you're in Reconstruct Mode. Do you find yourself having to refresh your browser when FoE has been sitting idle in Chrome for a while? I do at times. I've collected buildings before, refreshed my browser and have had to collect all over again.I'm pissed off! Sorry for the rise in temper. You see, I spent more than 2 hours reconstructing my city and when I click on 'SAVE', the PC (or rather Google Chrome froze). When I restarted - nothing changed, it was my old city. So, I tried reconstructing all over again (for the second time!) Spent 3 hours and again when I click on 'SAVE', it was deja vu. Chrome froze and now I'm still stuck with my old city. Don't really mind though but what pissed me off was wasting more than 5 hours for nothing!
Unless, I get real help from the Manager or whoever, I shall give up the idea of reconstructing!