Puzzling Error Message

[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...

[Foodstamp]

I think your right. WOW, I made a waterbound nation and did not give them the ability to build underwater forts. I copied and pasted the forts from a land based nation, changed the land forts but never added the water ones, simply WOW. I am going to fix it and test it again, thanks for the help.