This story from SpaceDaily, originally reported on Doug's Unmannedspaceflight.com, which I can't get to now, apparently this article has sent alot of new visitors Doug's way.

NASA's Mars Exploration Rover Opportunity has experienced a significant breakdown with the suspected failure of the front right wheel motor.According to a report posted on Doug Ellison's renowned Mars forum Unmannedspaceflight.com, "Opportunity's right front steering actuator stalled near the end of the drive on sol 433 (after 150 meters of driving).

"On sol 434, they backed up a meter or so and tried to straighten the wheel, but the steering motor stalled again without moving at all. Imaging doesn't show any reason for the stall. The wheel is about 7 degrees off from straight, which would still be driveable if they can't resolve the problem."