I have an overclocked i5 and I don't get anything at all for like 40 minutes, did you add something extra?
Nope. Compiled on Ubuntu, running on a 30 MB/s cable connection (over WiFi).
I had a 22 minutes dry spell between 11:10 and 11:32, then got four blocks between 11:41 and 11:42. It's quite random.