Anyhow, I promised Selax I'd write up a topic detailing a few ideas I had while he and I were chatting on IRC a few nights ago. Nothing big, and of course those of you who read this can throw it out if you choose. They're just thoughts.
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From what I've seen and read, you're suffering from either lack of interest or lack of participation. So I got to thinking, "what could solve that?"
One possibility is that you could have someone play the role of a 'Game Master' or such. They set up the situations, they lead the party (but aren't actively playing) into and out of trouble, they basically are responsible for the story. Input can come from individuals who are playing along, but by and large the GM leads everyone. Those playing choose how to react to each situation.
Selax mentioned every one of you should create new characters. Why not? All new investment, you get the opportunity to creative, and you're not stuck in a rut. Along with that, don't create overpowered heroes that can just swat trouble away with a wave of your hand/wand/sword/pick your weapon. Try limiting your powers, or have no powers at all, so you have to solve puzzles creatively.
I don't know if you've ever done this (probably have) but do all the players travel together, or do groups occasionally separate to do more than one task? And do you all have multiple characters, or just one? I'd limit it to just one to avoid burnout, if you don't already work that way.
Next step: ???
Then: profit! er, no. Haha.
That's all I've got for now, feel free to fall upon it like rabid dogs.