Unreal engine 5.1 crashes on startup

Development Getting Started & Setup
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1

I recently updated from 5.0.3 to 5.1.0, but now it wont start. It stops at 75% and then the crash reporter spits out this:

Unhandled Exception: EXCEPTION_ACCESS_VIOLATION reading address 0x0000000000000000

UnrealEditor_UdpMessaging
UnrealEditor_UdpMessaging
UnrealEditor_UdpMessaging
UnrealEditor_Messaging
UnrealEditor_UdpMessaging
UnrealEditor_UdpMessaging
UnrealEditor_UdpMessaging
UnrealEditor_UdpMessaging
UnrealEditor_Core
UnrealEditor_Projects
UnrealEditor_Projects
UnrealEditor_Projects
UnrealEditor
UnrealEditor
UnrealEditor
UnrealEditor
UnrealEditor
UnrealEditor
UnrealEditor
kernel32
ntdll

Version 5.0.3 still launches, as does 4.27.2. I have rebooted, updated graphics drivers, reinstalled, reinstalled on another drive and googled a lot.

Any idea as to what is causing my crashes?

2

Hi Branden,

UdpMessaging is a plugin that’s enabled by default. Since your logs mention this plugin trying to turn it off could be a good first step. (But before turning off UdpMessaging, try disabling any other third party plugins you may have added)

To deactivate plugins without launching the editor - open up your .uproject file with a text editor.

			"Name": "UdpMessaging",
			"Enabled": false

Welcome to the Forums. Let us know if that makes any difference!

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3

That helped! But, sadly, only with that specific project. If i try to launch the engine through the Epic Games launcher without any specific project it still gives the same crash report.

4

Glad to hear it!

Yeah, a crash when launching engine through launcher would be expected since it’s a default plugin.

Here’s a thread that shows how to change info in the overall engine’s .ini.

Also someone in that thread resolved it by restarting their PC!

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5

Hey, I started the other thread. I’m glad we’re getting more eyes on this problem because it’s a pain in the butt to have to deal with for every project. Windows isn’t blocking the UDP plugin, neither is my router’s firewall. No official responses from Unreal concerning this issue. Might be good to increase the urgency on it, given I’m not the only one running into this.

6

Ahh oops! If you haven’t already, submit a bug report for this. Also request that this bug be made public (so it shows up on issues.unrealengine.com and people can vote it up)

7

I could not solve it like it was done in the other thread, but I did solve it!

To make Unreal Engine 5.1 launch again (for me at least):

  • Go to C:\Program Files\Epic Games\UE_5.1\Engine\Plugins\Messaging\UdpMessaging

  • Open “UdpMessaging.uplugin” with notepad

  • Change “EnabledByDefault” to false instead of true

But people managed to solve it the other way in the other thread, but this might be an alternative if it does not work.

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