From the Wizards.com blog.
This obviously raises many more questions than answers. If the X-ray is negative, what exactly is the problem? Why can't the Wizards training staff diagnose it? Why does it get worse when Caron sits on it too much? Does the nature of Butler's game make such an injury more painful than a thumb? Why is Butler showing flashes when he's hurt?
Basically, it proves nothing, and with the time most important, it's not good news to hear. I'd almost rather hear that he's legitimately hurt. At least the Wizards will know that they need to compensate during the stretch run.
Update [2007-3-16 15:17:8 by Pradamaster]: They're now saying that Caron is expected to be out 7 to 10 days with a knee contusion. Seth brought up a great point in the comments section about how training staffs need to be careful with this kind of thing. Hopefully, Caron can just sit out this week and feel completely healthy again.