It's really hard to say where the problem came in, without having witnessed the actual brew session. My knee-jerk reaction is to say that the yeast was probably not good. I'm curious about this statement:

erikrocks wrote:--though it was still foamy at the bottom when I pitched it.

Usually, when I have healthy rehydrated yeast in a cup, there is a frothy, foamy layer on top of the slurry. At least, that is my experience with rehydrated dry brewing yeast, and I don't claim to be an expert. I've had several packages of bad yeast, and what seems to happen with these is, the yeast doesn't rehydrate very well, and clumps up at the bottom. A lot of the yeast 'beads' (for lack of a better word), sink to the bottom and never seem to liquefy. It doesn't look foamy or frothy to my eyes though.

Using tap water to top off your carboy shouldn't have caused your yeast to die off. I've rehyrdated yeast in tap water numerous times, and if that doesn't kill them, then a little tap water mixed in the rest of your beer definitely shouldn't. I would steer clear of topping off with straight, unboiled tap water for other reasons, though.

If you pitched the yeast while your wort was still hot, it's possible that they were scalded to death.

Like I said, it's hard to say with any sort of conviction what the problem was, without actually being there during the brew, but bad yeast and pitching too hot seem to be the most common causes for dead yeast.

I hope you have no other problems, and end up with a great beer!

Cheers,
Dave

Well, I pitched the generic dry ale yeast (without rehydrating) last night and...BUBBLES!!!!

GREAT! Let us know how the beer turns out!

Cheers,
Dave

What was the temp of your wort when you pitched the yeast? If it was over 100F you could have killed off the yeast...

The wort was 80 degrees when I pitched the first time--i made sure not to kill the yeast by pitching too early.

Coulda been bad yeast then.

Personaly I think yeast are terribly mysterious creatures and like to screw with us brewers.

Well, it's been 3 weeks, and I just took a hydrometer reading and...1.025. Ugh, I don't understand. Should I dump and start anew?