Thanks all for the suggestions. I THINK I set up the tension
correctly, but I am having other problems. I need some help
determining if they are related.

After I installed the new cables, I was able to tension them such that
the door opened and closed fairly smoothly without much effort. I
hooked up the opener and was able to open close 3 or 4 times with no
problem.

Then, I went to test it again later, and it kept getting stuck. I
tried pulling it up and down manually and noticed that it was randomly
and sticking in either direction. If I keep pushing or pulling, the
thing won't budge in these cases. However, if I let up on the
pressure, or briefly change directions, it'll usuall slide right
through whichever spot it was previously sticking on.

I don't see any obvious obstruction. The rollers all seem to roll,
and the thing is evenly in the tracks. What the heck else could it
be? The biggest difficulty here is that it seems to stick randomly,
in any given spot, going in either direction. I have to assume its
somehow related to the pull cables having falled off the tracks
earlier - seems like too much of a conincidence otherwise. Could this
be a problem with my tensioning, or some kind of damage from when the
cables were off the pulleys?

Thanks,
Jeff