My ethereum balance seems to be 0 when checked via geth

I created an ethereum address

geth account new

and sent some ethers to it. Then I ran the server:

geth

and the JavaScript console:

geth attach

I checked the balance, but it was 0:

> eth.getBalance('0xB97168a67AB66E55B98B1439222Ee665E657fFc0')
0

When I checked the balance via etherchain, there were some ethers.

What am I doing wrong?