From: east coast, usa
Hey Bill, and everybody else concerned, I may have found something of interest. I recently added a port [circled gold] to the 653H Mod and began receiving the oft reported error [inset]. I noticed that after I added this port the bottom of the screen [red highlight] read 'Port (Neutral)', while all other ports on the map report the owner of the hex. This actually has to do with the Hex Layer, not the Resource/Port Layer. I think that maybe hexes cannot be neutral. So in the Editor I went to Edit Hex Layer > Set Hex Owner/Controller, and that hex was not set to any country, so I set it to Portugal [in this case, and as it is seen in the shot below]. Voila ! No more error !
I no longer have your mod on my computer to check it, but if I remember correctly I always got this area around Malta. So maybe check the Malta hexes and make sure they do not read as 'neutral' in that red highlighted area in the sceen shot, and if they do, do the 'Edit Hex Layer > Set Hex Owner/Controller' thing to set it to UK.