I had the same problem when setting up the miner. There seems to be a problem with the most recent version of bitcoin (0.3.22-beta). Try version 0.3.21-beta and it should work - given that the rest of your setup is okay.
What, seriously? Thats bad.
Well, it might not be good, but it
is progress.
Now -- using the previous version of the Bitcoin client, after reporting that it's added the GPU, it has started throwing "Can't connect to Bitcoin: Connection refused: connect" errors. It throws a bunch (~12) of them with "waiting..." between the first several and then khash/sec figures between them for a while (in the 11-13000 range) and then reports the fatal error and drops out of running.
I'm launching the app with the -u and -p flags each followed by the values in the bitcoin.conf file. Am I supposed to be doing something different because I'm using 0.3.21 now?