SOCedit crashes...

I clicked on one of the following buttons: HUD editor, Edit Sounds, Edit Level Headers, Edit things, Edit Cutscenes, and Edit States on SOCedit, and it gives me a runtime error 53: File not found error. What do I do, and is there an updated version?

Are you using the one supplied with SRB2 2.0?

Did you extract the source code and point the program to it?
Read about it here: http://wiki.srb2.org/wiki/SRB2_SOC_Editor

Well even without the source code people can still edit level headers.

Ya. Create a MAINCFG text lump in SLumpEd or XWE and type it in there. It's like:

level 1
levelname = slime base
act = 1
musicslot = 137
nextlevel = 2
typeoflevel = 4096
weather = 1
skynum = 10
timeattack = 1
levelselect = 1

But insert all of your own specs and stuff. If you just copy this, the level will load, say "SLIME BASE ZONE 1," start playing the Tempest Valley music, create an CEZ1 sky, and start raining.

Thank you Kyasarin. That worked.