I fixed this by correcting the entry for Researches.AdvancedLasers in the researches.xml file (located in the assets folder in your install directory). The entries in the "When Finished" column were not correct. They were missing the "UpgradeBuilding("MissileTurret", "LaserTurret");" item. The full entry in the "When Finished" column should be:
UnlockKnowledge( "Researches.RapidFireLasers" );
UnlockManufacture( "ManTech.Scatterlaser" );
ReplaceItem("AV.AUTOCANNON","AV.SCATTERLASER");
UnlockItem("VV.PULSELASER");
UnlockKnowledge( "Researches.PulseLasers" );
UnlockBuilding( "LaserTurret" );
UpgradeBuilding("MissileTurret", "LaserTurret");
If you make sure that all these items are present, then hopefully your heavy laser resaerch should complete successfully. Good luck!
