I have done some searching on this and found things saying to turn off Windows Defender and also a post saying to run bcdedit.exe...AlwaysOff from an administrative command prompt.  I've done these things but still get this incredibly irritating error from time to time.  Does anyone have any ideas what else I can try?  My O/S is Win7 and using P3D v4.1 with 99% of my flights in the FSLabs A320 if any of that info helps.

Thanks.  This is so frustrating.  :(

According to the AVSIM CTD Guide, page 35:

NTDLL.dll – Several possibilities for the NTDLL.dll error are as follows:

• Most probable cause is outdated or corrupted hardware drivers.  Run a driver update program as discussed in previous section.
• Use the System File Checker (SFC \scannow) to look for corrupt or missing system files.  See previous section for details on running this program.
• Recently update video card drivers?  Reinstall or install the previous version.
• System overheating.  Check (not common but it can cause this crash).
• Wrong timings/voltages set for your installed RAM. 
• CPU voltage too high or too low (only if you overclocked your computer, manually or professionally by a computer expert). You might be able to fix by returning your BIOS to Optimized Defaults or lowering the overclock by one point from say, 4.4GHz to 4.3GHz.
• Windows 7 users - Remove the UIAutomationcore.dll from the main FSX folder, if installed (applies to FSX users only).  A known fix (could be the wrong version placed in the FSX folder).  Do not remove for FSX-SE or Windows 8/10 users.
• Check your dll.xml for duplicate entries or entries where the software was removed but the entry in the dll.xml still exists.  Fix.
• Disable User Access Controls (UAC) (see the section above for more information).
• MyTrafficX, v5.4c possibly caused by an AI scheduling programming error. Go back to the 5.4b version.  Check developer’s forum for possible fixes.
• For MyTraffic6, rename MyTrafficmil.bgl to MyTrafficmil.OFF in your MyTraffic/Scenery folder. 
• Changing aircraft from payware to default and vice-versa.