Crash on shutdown. Then crash on start

Dear all,

I encountered a problem when I was closing my project. During (or maybe shortly after) saving my project before shutting down the editor, the editor stopped responding. The taskmanager showed continous hard drive activity of the editor. Also the memory grew steadily. I killed the process shortly before the system memory was full (16GB).
When I now try to open the project the editor crashes with the following Callstack:

Unknown exception - code 00000001 (first/second chance not available)

Fatal error: [File:D:\BuildFarm\buildmachine_++depot+UE4-Releases+4.6\Engine\Source\Runtime\CoreUObject\Private\Templates\Casts.cpp] [Line: 11]
Cast of nullptr to Blueprint failed

KERNELBASE + 24684 bytes
UE4Editor_Core + 3092349 bytes
UE4Editor_Core + 1597391 bytes
UE4Editor_CoreUObject + 369143 bytes
UE4Editor_Engine + 1794732 bytes
UE4Editor_Engine + 2068206 bytes
UE4Editor_BlueprintGraph + 836216 bytes
UE4Editor_BlueprintGraph + 833829 bytes
UE4Editor_BlueprintGraph + 808036 bytes
UE4Editor_BlueprintGraph + 808110 bytes
UE4Editor_BlueprintGraph + 1023675 bytes
UE4Editor_BlueprintGraph + 608017 bytes
UE4Editor_UnrealEd + 9619647 bytes
UE4Editor_UnrealEd + 9621607 bytes
UE4Editor_CoreUObject + 626800 bytes
UE4Editor_CoreUObject + 946322 bytes
UE4Editor_CoreUObject + 1054484 bytes
UE4Editor_CoreUObject + 878004 bytes
UE4Editor_CoreUObject + 686086 bytes
UE4Editor_CoreUObject + 1094210 bytes
UE4Editor_CoreUObject + 946764 bytes
UE4Editor_CoreUObject + 1054484 bytes
UE4Editor_CoreUObject + 944791 bytes
UE4Editor_CoreUObject + 947419 bytes
UE4Editor_CoreUObject + 1062891 bytes
UE4Editor_CoreUObject + 1460613 bytes
UE4Editor_CoreUObject + 1193007 bytes
UE4Editor_CoreUObject + 1189666 bytes
UE4Editor_CoreUObject + 1193874 bytes
UE4Editor_CoreUObject + 1189666 bytes
UE4Editor_CoreUObject + 1189156 bytes
UE4Editor_CoreUObject + 976397 bytes
UE4Editor_CoreUObject + 1185872 bytes
UE4Editor_CoreUObject + 951800 bytes
UE4Editor_CoreUObject + 1026078 bytes
UE4Editor_CoreUObject + 1460171 bytes
UE4Editor_UnrealEd + 2768012 bytes
UE4Editor_UnrealEd + 2700861 bytes
UE4Editor_UnrealEd + 2612749 bytes
UE4Editor_UnrealEd + 6316416 bytes
UE4Editor_UnrealEd + 3168772 bytes
UE4Editor_UnrealEd + 3167944 bytes
UE4Editor_UnrealEd + 6555369 bytes
UE4Editor_UnrealEd + 6310846 bytes
UE4Editor!GuardedMain() + 285 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.6\engine\source\runtime\launch\private\launch.cpp:123]
UE4Editor!GuardedMainWrapper() + 26 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.6\engine\source\runtime\launch\private\windows\launchwindows.cpp:126]
UE4Editor!WinMain() + 249 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.6\engine\source\runtime\launch\private\windows\launchwindows.cpp:202]
UE4Editor!__tmainCRTStartup() + 329 bytes [f:\dd\vctools\crt\crtw32\dllstuff\crtexe.c:618]

Can somebody help me with the problem?

Edit: I tried a few things and found a blueprint that might be corrupt. I can start the editor when I remove the blueprint.uasset from the content folder. I can copy it back in once the editor runs but as soon as I try to open the blueprint the editor crashes. I also tried replacing the blueprint with one of the backups in the saved/backup directory. The result is the same.

Regards

I solved the problem.

Apparently one of my blueprint interfaces was corrupted. I could however import the blueprint in an empty project and then recompile it. After that I was able to copy the .uasset file back to my original project without causing crashes.