A couple of things...

You need an updated client. You should see
    "version": 32463
You can get the current client at dot-bit.org - this will let you see blocks higher than 19200.

If you are mining at Slush's pool, you don't actually need the namecoin client, except to receive your namecoin reward when it is distributed. Just use your usual miner in the usual way.

At some point you will need to do
to get an address for your namecoin rewards, but that's about it.