The "real" solution would be convincing AI modelers to create native FSX models.
The issue only happens with 3rd party FS9 AI models imported in FSX, and only when the airport is using FS9-styled ground polygons with runways lights on top of it. For unknown reasons, this technique that worked in FSX SP1, creates problems with AI traffic in SP2, but *only* if the AI models are of the FS9 type. Right now, we don't have a solution to fix this from our side, it's simply look like some part of FS9 backward compatibility that has been lost from SP1 to SP2.
A workaround is to delete the file that creates runways lights but, of course, even if this would work, it's not an ideal solution, because it would force losing runway lights. That's why the correct way to solve this, would be using native FSX models as AI. Zurich (and Aerosoft Heathrow that has the same issue) works fine with FSX standard AI traffic, because the models are FSX native.
I also think that using fps friendly AI models compiled for FSX, would increase performances as well, both comparing to MS default AI traffic, and to old FS9 models imported in FSX.