Richard Durrett has a blog post up about Chris Davis, that includes some good quotes from Davis and Rudy Jaramillo:
Hitting coach Rudy Jaramillo said Davis' problems is "all mental.""When his mind isn't right, it can cause problems with his mechanics," Jaramillo said. "It's all mental for him. Young hitters go through this and I am confident he's going to hit. This may be the first time he's really failed and it's happening at the major-league level. We have to stay patient."
I'd encourage you to read Durrett's full post, which includes Rudy saying that Davis needs to stay up here and work through these issues at the major league level, rather than at the minor league level.
Davis has tended to be streaky -- he was incredibly bad in his first month or so as a professional, then got going, then was hot for most of 2007. In 2008, he was great his first month in the majors, slumped badly his second month, and then was great again in September.
If Rudy says it is mental and something that Davis needs to address while getting big league ABs, that's good enough for me...I'd be willing to sacrifice a little bit of performance for the major league club right now if it means helping Davis's development long-term, and besides, if you send Davis to AAA (as some suggest), you are basically making Hank Blalock your everyday first baseman, which I think isn't necessarily a net gain.