On September 4, 1996, at 2025 hours Pacific daylight time, a Cessna 425, N425WB, landed on runway 07 at the (uncontrolled) Auburn Municipal Airport, Auburn, California. According to the pilot, he lost control of the airplane during rollout. The airplane veered left off the runway and was substantially damaged. Neither the commercial pilot nor passenger was injured. Visual meteorological conditions prevailed at the time, and an instrument flight rules flight plan was filed. The business flight originated from the Snohomish County Airport (Payne Field), Everett, Washington, at 1800. The pilot reported that the airplane touched down within the first 1/4 of the runway, and he applied full reverse thrust. The application of reverse thrust was discontinued as the airplane approached the last 1/3 of the runway, and firm braking was initiated. As the brakes were applied the airplane veered left, and the "right (rudder) peddle went to the floor." The pilot further reported that he tried steering using the rudder but had little success. About 3/4 of the way down the runway, the pilot feathered the right engine's propeller and applied power to the left engine. Despite these efforts, the airplane continued veering toward the left side of the runway, and it eventually went into a ditch, collapsing the nose gear. The airplane's brake system was examined by a mechanic from PassTime Aviation, Auburn. According to PassTime's general manager, the right brake pads and disc were found in good (serviceable) condition. The O-rings in the brake housing had a distorted shape. When the brake system was pressurized, hydraulic fluid leaked past the O-rings. New O-rings were installed in the right brake assembly and it was pressurized. No leaks were noted, and the brake system then appeared airworthy. The airplane was maintained on an approved inspection program. Its last inspection was performed about 110 hours prior to the accident flight.