Sounds like a file is corrupt.. take your local folder out of the myth folder and try opening Loathing. if it works, go through and take out a couple files within the local folder at a time until you find the bad file. if it still doesn't work, try looking through your plugins folder. I remember i accidently put a simpletext file in there once, and loathing wouldn't work until i took it out.
Also, if it quits when you try to open a map, make sure it's bigger than 512x512.