UDK wont build lighting anymore. [SOLVED]

I've never seen that and I've got some pretty large levels.

Are you having issues with a new level or only in custom levels?

I'd try these things if it is happening with a new level:
1. Try switching between Dx9 & Dx11 to see if anything changes.
2. Try playing a UDK built level to see if it at least the level works.
3. Worse case, backup all your projects/maps, uninstall UDK, delete the UDK directory and then reinstall.

Hey thanks for your reply.

I tried the default scene, but same problem there. Any custom scene I made also have the problem. I cant switch to DX11 or DX9 because the "switch renderer" button is grayed out :(.
I did already reinstall UDK, but The problem is still there. It is really strange.

I just tried to build again and after some time waiting I got this error message:

19:31:39: [Interface:TryOpenConnection] Local connection established
19:31:39: [Job] Accepted Job E162C256-4717C129-30E8699E-4A7E32B7
19:31:40: [Interface:CacheAllFiles] Failed to cache the executable: ..\Win32\UnrealLightmass.exe
19:31:41: [Job] AddTask: Rejected, cannot add a task to a running job
19:31:41: [CloseConnection] Closing connection 7F0AA4BE using handle 7F0AA4BE
19:31:41: [CloseConnection] Connection confirmed for disconnection 7F0AA4BE
19:31:41: [CloseConnection] Closing orphaned Job (E162C256-4717C129-30E8699E-4A7E32B7)
19:31:41: [CloseConnection] Connection disconnected 7F0AA4BE
19:31:41: [GetMessage] Safely returning to 7F0AA4BE with no message
19:31:43: [MaintainConnections] Local connection has closed (7F0AA4BE)
19:31:43: [MaintainConnections] Removed connection 7F0AA4BE
19:31:43: [MaintainConnections] All connections have closed

I know it can be frustrating when you can't get help with UDK.

My #1 resource is the chat channel for UDK:
irc.web.gamesurge.net
channel #UDKC

My nick is parzival, but I'm usually (always) asking for help instead of giving it.

There are only a couple of dozen folks there but they have got me out of a tight spot with UDK half a dozen times.

I'm getting the impression from searching the web it is a memory issue.

I'd keep digging around the web on "Failed to cache the executable UnrealLightmass.exe:

This looks promising:
http://forums.epicgames.com/archive/index.php/t-955514.html

discussion of interest:
-------------------------------
It's possible that you've run out of ram. Are you running 64-bit Editor?
DaPPa

I didn't know there was a 64 bit editor?

The lightmass ran this time, it must have been a pagefile problem, I set both my SSD and main drive to 12gb pagefile for now and it ran ok, although my skydome has a really big weird shadow on it, also my landscape keeps flickering in and out because I moved it.

Thanks for the help guys.
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Hey thanks for your reply!

A memory issue might be the problem. People on the forums keep mentioning a too filled up hard disk. My hard disk is quite full. I installed UDK on disk D, and tried building. It worked, but it took a very long time. A few minutes just to build the start up default scene.

Ok It works again :D ! I changed some settings in the swarm agent like this guy described in his post: http://forums.dungeondefenders2.com/archive/index.php/t-66533.html (last post on the page). I don't know what exactly the problem was, but now it works again :).

Great to hear you found a solution. Sorry I could not have been of more help.

Hey no problem. It was a kind of an uncommon problem I guess. So no one really knew the solution :D.