Unable to upgrade project to 4.2, crash on startup

Hi guys, having some trouble upgrading my project to 4.2. Works on 4.1, crashes on startup on 4.2. Seems to be specific to my project because others seem to work fine. Here’s the crash report:

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

Assertion failed: Class [File:D:\BuildFarm\buildmachine_++depot+UE4-Releases+4.2\Engine\Source\Runtime\CoreUObject\Public\UObject\Class.h] [Line: 2377]
ConstructObject called with a NULL class objec

KERNELBASE + 23544 bytes
UE4Editor_Core + 2998748 bytes
UE4Editor_Core + 1620298 bytes
UE4Editor_Core + 1561376 bytes
UE4Editor!FEngineLoop::Init() + 272 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.2\engine\source\runtime\launch\private\launchengineloop.cpp:1855]
UE4Editor_UnrealEd + 5156540 bytes
UE4Editor!GuardedMain() + 285 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.2\engine\source\runtime\launch\private\launch.cpp:124]
UE4Editor!GuardedMainWrapper() + 26 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.2\engine\source\runtime\launch\private\windows\launchwindows.cpp:125]
UE4Editor!WinMain() + 249 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.2\engine\source\runtime\launch\private\windows\launchwindows.cpp:207]
UE4Editor!__tmainCRTStartup() + 329 bytes [f:\dd\vctools\crt\crtw32\dllstuff\crtexe.c:618]

See attached log file.

link text

Probably posted in wrong section, reposting under bug reports.

Closing as duplicate. Gigantoad re-posted this on Bug Reports section. Unable to upgrade project to 4.2, crash on startup - Platform & Builds - Unreal Engine Forums