[ale] (Somewhat OT) Blown circuit breakers?

[rekoil at semihuman.com (Chris Woodfield)]

As I'm sure there are a few folks with electrical experience here...

I'm in the middle of a bathroom remodeling project, and yesterday my  
wife was putting down drywall mud around an electrical box that had  
live wires coming out of it (yeah, I should have capped them...), and  
accidentally shorted them with a mudding knife, which tripped the  
circuit breaker. She reset the breaker, and carried on...until later  
that night, I did the same exact thing. However, this time the power  
did not come on when I reset the breaker, and every outlet/light  
attached to that breaker is now dead.

I've never heard of a "blown" circuit breaker before, so is that what  
I should replace first (It's a 15A single-pole breaker)? Or should I  
be looking at a possibly melted wire somewhere in my wall? I'm going  
to replace the breaker, as they're cheap, just looking for other  
possible problems this could have caused.

Thanks,

-C