UMG - Editor crash on opening any widget in 4.10

Opening any widget, even a newly created one results in the engine crashing instantly.
The project I’ve been working on and all the associated widgets do work just fine, I simply can no longer edit them.

This issue affects blank projects as well. The editor has been reinstalled twice.
[EDIT1: The existing widgets work but cannot be edited. Also, no issues in 4.9.2 ]
[EDIT2: Similar issue: Crash when opening Blueprint for UI - Blueprint - Unreal Engine Forums]

To repro:

  1. Create a new blank project in 4.10
  2. In the content browser: Add New → User Interface → Widget Blueprint
  3. Double click the newly created widget to open

Result:
Editor crashes with the following message:

Unknown exception - code 00000001 (first/second chance not available)
"Assertion failed: IsValid() [File:D:\BuildFarm\buildmachine_++depot+UE4-Releases+4.10\Engine\Source\Runtime\Core\Public\Templates\SharedPointer.h] [Line: 739]
"
UE4Editor_Core!FDebug::AssertFailed() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\runtime\core\private\misc\outputdevice.cpp:374]
UE4Editor_UMGEditor!FWidgetBlueprintEditor::UpdatePreview() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\editor\umgeditor\private\widgetblueprinteditor.cpp:680]
UE4Editor_UMGEditor!FWidgetBlueprintEditor::InitWidgetBlueprintEditor() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\editor\umgeditor\private\widgetblueprinteditor.cpp:86]
UE4Editor_UMGEditor!FAssetTypeActions_WidgetBlueprint::OpenAssetEditor() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\editor\umgeditor\private\assettypeactions_widgetblueprint.cpp:32]
UE4Editor_UnrealEd!FAssetEditorManager::OpenEditorForAsset() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\editor\unrealed\private\toolkits\asseteditormanager.cpp:311]
UE4Editor_UMGEditor!FAssetTypeActions_Base::AssetsActivated() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\developer\assettools\public\assettypeactions_base.h:41]
UE4Editor_ContentBrowser!SContentBrowser::OnAssetsActivated() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\editor\contentbrowser\private\scontentbrowser.cpp:1757]
UE4Editor_ContentBrowser!TBaseSPMethodDelegateInstance<0,SContentBrowser,0,TTypeWrapper cdecl(TArray const & ptr64,enum EAssetTypeActivationMethod::Type)>::Execute() [d:\buildfarm\buildmachine++depot+ue4-releases+4.10\engine\source\runtime\core\public\delegates\delegateinstancesimpl_variadics.inl:282]
UE4Editor_ContentBrowser!TBaseSPMethodDelegateInstance<0,SContentBrowser,0,void cdecl(TArray const & ptr64,enum EAssetTypeActivationMethod::Type)>::ExecuteIfSafe() [d:\buildfarm\buildmachine++depot+ue4-releases+4.10\engine\source\runtime\core\public\delegates\delegateinstancesimpl_variadics.inl:388]
UE4Editor_ContentBrowser!SAssetView::OnListMouseButtonDoubleClick() [d:\buildfarm\buildmachine
++depot+ue4-releases+4.10\engine\source\editor\contentbrowser\private\sassetview.cpp:3292]
UE4Editor_ContentBrowser!TBaseSPMethodDelegateInstance<0,SAssetView,0,TTypeWrapper cdecl(TSharedPtr)>::Execute() [d:\buildfarm\buildmachine++depot+ue4-releases+4.10\engine\source\runtime\core\public\delegates\delegateinstancesimpl_variadics.inl:282]
UE4Editor_ContentBrowser!TBaseSPMethodDelegateInstance<0,SAssetView,0,void cdecl(TSharedPtr)>::ExecuteIfSafe() [d:\buildfarm\buildmachine++depot+ue4-releases+4.10\engine\source\runtime\core\public\delegates\delegateinstancesimpl_variadics.inl:388]
UE4Editor_ContentBrowser!TBaseDelegate >::ExecuteIfBound() [d:\buildfarm\buildmachine
++depot+ue4-releases+4.10\engine\source\runtime\core\public\delegates\delegatesignatureimpl_variadics.inl:482]
UE4Editor_ContentBrowser!SListView >::Private_OnItemDoubleClicked() [d:\buildfarm\buildmachine
++depot+ue4-releases+4.10\engine\source\runtime\slate\public\widgets\views\slistview.h:689]
UE4Editor_ContentBrowser!STableRow >::OnMouseButtonDoubleClick() [d:\buildfarm\buildmachine
++depot+ue4-releases+4.10\engine\source\runtime\slate\public\widgets\views\stablerow.h:261]
UE4Editor_Slate!::operator()() [d:\buildfarm\buildmachine
++depot+ue4-releases+4.10\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:4609]
UE4Editor_Slate!FEventRouter::Route >() [d:\buildfarm\buildmachine
++depot+ue4-releases+4.10\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:214]
UE4Editor_Slate!FSlateApplication::ProcessMouseButtonDoubleClickEvent() [d:\buildfarm\buildmachine
++depot+ue4-releases+4.10\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:4607]
UE4Editor_Slate!FSlateApplication::OnMouseDoubleClick() [d:\buildfarm\buildmachine
++depot+ue4-releases+4.10\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:4590]
UE4Editor_Core!FWindowsApplication::ProcessDeferredMessage() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\runtime\core\private\windows\windowsapplication.cpp:1346]
UE4Editor_Core!FWindowsApplication::DeferMessage() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\runtime\core\private\windows\windowsapplication.cpp:1709]
UE4Editor_Core!FWindowsApplication::ProcessMessage() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\runtime\core\private\windows\windowsapplication.cpp:707]
UE4Editor_Core!FWindowsApplication::AppWndProc() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\runtime\core\private\windows\windowsapplication.cpp:629]
user32
user32
UE4Editor_Core!FWindowsPlatformMisc::PumpMessages() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\runtime\core\private\windows\windowsplatformmisc.cpp:884]
UE4Editor!FEngineLoop::Tick() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\runtime\launch\private\launchengineloop.cpp:2391]
UE4Editor!GuardedMain() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\runtime\launch\private\launch.cpp:142]
UE4Editor!GuardedMainWrapper() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\runtime\launch\private\windows\launchwindows.cpp:126]
UE4Editor!WinMain() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\runtime\launch\private\windows\launchwindows.cpp:200]
UE4Editor!__scrt_common_main_seh() [f:\dd\vctools\crt\vcstartup\src\startup\exe_common.inl:264]
kernel32
ntdll

Resolved by resetting window layout: