The obvious, non-conspiratorial answer...

...to the much-bandied question of why the White House waited 18 hours to mention that Dick Cheney accidentally shot a guy, is that they were hoping it would distract from the House committee's report on Katrina. That would be an all-Republican committee, reporting that the White House completely screwed up and failed to prevent several hundred deaths. Wouldn't anyone rather that people were tittering about possible cover-ups of a non-fatal hunting accident?