QTCore4.dll isn't actually a DAZ file, it's a C++ library file. Windows loads system components with it. If I had to bet, I'd say you have a version of it somewhere on your computer that doesn't match what DAZ is expecting. I'd do a scan for that file on your computer, and if you find multiple copies, send DAZ the information on what the version numbers are and where they are stored on the machine (the directories). With DLL's, the first one to be loaded wins, so if you have multiple versions what program you are running will determine which one is loaded in memory which can make it tough to track down the problem.