[Endoperez]

Could it be linked to this:

21st april
* Version 3.07
* Dragonflies' strength changed from 0 to 1 and they can now inflict damage.
* Burden of time caused severe damage to diseased non old people, fixed.
* LA Atlantis could not continue fort construction, fixed.

I'm not sure what it did, but "build f" sounds like a problem with fort-building...