The error is probably not in SLumpEd; it's more likely in the WAD itself. First of all, I assume you're making a character WAD. Second, make sure all the frames are BMP files, not PNGs (I don't think this is a problem if you're using SLumpEd, but try it anyway). Third, and very importantly, you need to have every frame of the WAD already existing before you load it into SRB2 and test it. If you're not done and only have a few of the frames done, add placeholder frames. Fourth, be absolutely sure that PLAYA1 (Note: it may not be PLAY--it could be four other letters, but it'll always be either A1 or A0) comes DIRECTLY after your S_SKIN lump. Fifth, check your last two rotations, PLAYa(1-8) and PLAYb(1-8). The "a" and "b" HAVE to be lowercase, otherwise your character will crash if you jump and/or spring in the game.
There are a few other things that might have caused the error, but those things I've mentioned are the most common issues. Make sure you're following all of those things, and, if there's still a problem, tell it to us in the most specific way you can.
By the way, the error you're getting is actually spelled this way:
Signal handler (): segment violation
On this message board, we call this error a "Sigsegv".