Seems an obvious question, no?  I am running 2 GPU's at about 275mhash/second each.  I am running Bitcoin in server mode.  I previously was involved in pooled mining at bitcoin.cz and made 20 bitcoins.  I was apparently one who did find a block in one round, so things are working.  However, running locally, I have not yet hit a block of 50 and I have now gone over the average time to find a block on my own.  I do not have "generate coins" on in the application, which I do not want to do, since use of the CPU only slows down my 2 GPU's by over an amount added by the CPU.  So it's not on and I haven't generated a block for myself and I'm hoping that is coincidence.  I don't want to find out a week down the line, "Hey stupid, you have to turn on "generate coins" in the app."  It would seem you don't since it is doing the hashes and therefore working.

Be patient, young padawan.