What's wrong with my new chain?
 

So I broke a chain and took it to a shop to have a new one installed (I have no chain tool). Great! So I take it out and it seems that each time I stand up to climb up a hill and begin pedaling, the chain "slips". It doesn't jump to another gear, just makes a horrible noise and causes me to lose all my momentum. Very annoying. Anyone know what's going on and/or how to correct this (besides remaining seated throughout my ride)? Thanks!

Your cassette may be worn out as well. I'm surprised they didn't check that! Either that or your freehub is toast!

Regardless, take it back to the shop and see if they can fix it! Be nice, but let em know you feel they should've test ridden your bike and noticed this. You wont get the cassette for free, but maybe they'll put it on for you for nuthin!

L8R

Have a look at

http://www.branfordbike.com/chains/chains6.html#item3

In the long run, it is cheaper to replace chains regularly and make your cogs last longer.

While you are at it, make sure you have the correct width chain for your cogset. Although there is usually no problem, some 9-speed chains do not seat properly onto 8-speed cogs, and some 8-speed chains hang up on the edges of adjacent 9-speed cogs. If your old chain had elongated by more than 1/2-percent, then excess cog wear is likely, as the others have suggested.

Yep, definitly sounds like "the-new-chain-old-cassete-problem"
Follow a2psyklnut`s advice, and take your bike back to the shop.

Good luck,