Today I was flying practice instrument approaches in my 95 M20R. On the final approach at the outer marker, I dropped the gear. The gear came down and locked, But the circuit breaker popped and the gear unsafe light lit up. The gear horn warning also went off. The manual indicator on the floor was showing down and locked. I did a missed and climbed to check the problem. I reset the breaker, raised the gear without incident. Re-lowering the gear resulted in full extension once again with the breaker popping again at the bottom of the cycle and the gear unsafe light illuminating. Once again, the mechanical indicator on the floor showed down and locked. I ended up landing on a grass runway instead of the concrete for safety reasons and taxied back to my hanger. Is this a gear actuator swith failure? Adjustment issue? Gear was lubricated and checked in June at annual. Any advice would be helpful. Thanks!