When I get "stuck" I try one or both of the following methods for working through the problem:
1. Brainstorm plot ideas for the next scene, chunk, ending of the story. Brainstorm as many as I can, jotting down the key points. I aim for twenty. Usually around #12-15, I get the BEST idea on how to fix everything that's not working, the heavens open up and I can't write fast enough.
2. Figure out character motivation for the major character, and particularly those in the last (or next to last) scene I've written. For me, I often get stuck when I try to write characters in a way that's no true to them. When If force them, they may say they knew X character 4 years ago, but something's wrong. They wouldn't ahve known X under those conditions, or something. I figure out they're background and their role in the story to a greater depth, and, if this is the problem, then the damn break and the prose floods forth.
Either way, I keep working. I finish what I started. I hate, hate, hate having to abandon something I spent time and energy on. I work out and through the problem.
storylady-- there will always be more ideas for stories. But not all ideas are capable of being turned into stories. My advice on the "idea overload?" Jot them down, include the most important elements, and set them aside. If they are good ideas, they will wait their turn in the cue. (Or wait their turn to be abandoned part way through... ;-)