Hello,My name is Michael Sable and I am not a computer expert, so please take it easy on me. I am a pilot however, and I was up late trying to fix this problem with my very limited knowledge. I appreciate any help that can be offered.I am getting the following fatal error; pmdg_747400_main.dllMSFX will run fine on its own, but not when I run 400X. It asks me about trusted software on the initial run of 400X.The prompts include:PMDGOptions.dllPMDGEvents.dllPMDGSounds.dllPMDG_747400_ACS.DLL, OVERHEAD.DLL, and CENTER.DLLI read about the other DLL issues, but I did not see anything about this in particular.Thanks again,Michael

Michael,Welcome to the forums.Have you tried to uninstall and reinstall the 400X?Hope it helps,

Thanks for the response.I think I have found the problem. I removed my anti-virus/firewall program and replaced it with Symantec. All functions appear to work correctly now.The AV program must have been preventing 400X from communicating with MSFS X. My knowledge is limited, so I don't really understand it, but as long as it works it is OK with me.Peace