Without intending to revive that old thread I just want to say the answer helped me, too.
Airport: Aerosoft LIMC (Milan_Malpensa)
Error (trying to import gates): cannot locate the scenery file in the designated import source directory
Solution: Change the name of the airport folder missing the LIMC in the name under CustomScenery/ to include LIMC, and adjust the scenery_packs.ini accordingly (in my case automatically done by xOrganizer).
Thanks!