The problem is that this isn't intermittent. The port icons have just vanished completely. The ports are still there on the map, the structures are there in the 3D world, it's just the icons that have vanished. And it's not a question of virtual memory as it happens after a fresh re-boot of the pc with nothing else but critical systems running (and 3 gb of ram on board).

JCC

It may be a MOD issue, because those icons are taken from a .mis file which a mod might have modified.