Why is my game crashing? (Access violation: c000005)

When I open my editor, and hit play, the editor crashes and shows an error that appears to be engine related:

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

"Assertion failed: Class [File:d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\runtime\coreuobject\public\uobject\UObjectGlobals.h] [Line: 1098] 
NewObject cal

KERNELBASE
UE4Editor_Core!FOutputDeviceWindowsError::Serialize() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\runtime\core\private\windows\windowsplatformoutputdevices.cpp:95]
UE4Editor_Core!FOutputDevice::Logf__VA() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\runtime\core\private\misc\outputdevice.cpp:144]
UE4Editor_Core!FDebug::AssertFailed() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\runtime\core\private\misc\outputdevice.cpp:355]
UE4Editor_AIModule!NewObject() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\runtime\coreuobject\public\uobject\uobjectglobals.h:1100]
UE4Editor_AIModule!FAIModule::CreateAISystemInstance() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\runtime\aimodule\private\aimodule.cpp:59]
UE4Editor_Engine!UWorld::CreateAISystem() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\runtime\engine\private\world.cpp:770]
UE4Editor_Engine!UWorld::InitWorld() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\runtime\engine\private\world.cpp:821]
UE4Editor_UnrealEd!UEditorEngine::PostCreatePIEWorld() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\editor\unrealed\private\playlevel.cpp:3438]
UE4Editor_UnrealEd!UEditorEngine::CreatePIEWorldByDuplication() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\editor\unrealed\private\playlevel.cpp:3425]
UE4Editor_Engine!UGameInstance::InitializePIE() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\runtime\engine\private\gameinstance.cpp:146]
UE4Editor_UnrealEd!UEditorEngine::CreatePIEGameInstance() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\editor\unrealed\private\playlevel.cpp:2619]
UE4Editor_UnrealEd!UEditorEngine::PlayInEditor() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\editor\unrealed\private\playlevel.cpp:2289]
UE4Editor_UnrealEd!UEditorEngine::StartQueuedPlayMapRequest() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\editor\unrealed\private\playlevel.cpp:1005]
UE4Editor_UnrealEd!UEditorEngine::Tick() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\editor\unrealed\private\editorengine.cpp:1236]
UE4Editor_UnrealEd!UUnrealEdEngine::Tick() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\editor\unrealed\private\unrealedengine.cpp:366]
UE4Editor!FEngineLoop::Tick() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\runtime\launch\private\launchengineloop.cpp:2359]
UE4Editor!GuardedMain() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\runtime\launch\private\launch.cpp:142]
UE4Editor!GuardedMainWrapper() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\runtime\launch\private\windows\launchwindows.cpp:126]
UE4Editor!WinMain() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.8\engine\source\runtime\launch\private\windows\launchwindows.cpp:200]

Any ideas what may be causing this error?