Working save game with the city:

http://dl.dropbox.com/u/4996295/Glorianna03.EleSav

After building some huts to the east of the city, the border broke:

But got fixed when I destroyed the watchtower that had been there since turn 5 or so:

To get broken again in the west when I built more stuff some turns later:

I haven't been able to repeat this. The only special thing could be that I had to load that game many times, reaching one point in which all the buildings appeared as "being built" (corrected itself some load games later). But as I said, I haven't been able to repeat it and other load games (of otehr games) have work well.