So this was kinda expected this, what with the problems at Mammoth and the high snow levels, but I was really hoping it wouldn't happen: 2006 Mountain Bike Nationals to Relocate. Basically, they can't have the 2006 MTB Championships at Mammoth due to snow levels (since they moved up this year's date to July) and are looking for a new venue. They'll keep the same July 20th date.
I really hope that this stays in Cali, but I bet that it moves to Colorado or Utah (pure conjecture on my part).
UPDATE (05/11/06): Okay, it stayed in Cali, but moved to the Cougar Mountain date and location. See here for details.