Hashrate is 2.2GH/s. When I connected to bitminter it accepted 6,500 shares, so it confuse me why it only accept so few and so many get discarded. Should I lower the difficulty to make it accept more?
Bitminter uses a lower default difficulty (4 I think) so that would explain it. If you're not using dynamic difficulty with Ozcoin, I recommend setting it to 2. If you stick with dynamic, it should settle down eventually.