Well, (based on what you're saying about your writing history, which I'm sorry if I'm misinterpreting) I would recommend writing three new short stories, and joining critters or OWW (I'm biased in favor of OWW). Put the new stories (one at a time) up on critters or OWW and hear what people have to say, and then rewrite them, which should give you some experience at rewriting.
Set those three stories aside, and then look with fresh eyes at the draft of the story that's been haunting you. Read it over, and then set it aside, too. Take a notebook and work through some plot exercises, for instance:
1) Write down 10 things that could happen in this story. Pick three that are interesting. Expand each of these three into a short scene.
2) A new character arrives. What happens? Freewrite.
3) A new threat arrives. What happens? Freewrite.
4) The story suddenly reverses direction in the middle. What happens now? Freewrite.
And see if anything clicks.
I'd probably leave the original text aside, and then try rewriting from scratch. Otherwise, you can get too sentimentally attached to preserving old phrasing or old ideas which were part of the problem in the first place.