There seems to be a few things I don't understand about the preview bus.
1. The clips in the audio library appear to be recorded super hot. I turned the input gain on the preview bus down to -9.0db and set the channel fader to -3db but most of the kick one shots show -8.5db on the bus output meter. How is that possible?
2. There are some clips that appear to have weird digital sounding artifacts when played through the browser, for example: Kick_015.wav in the One Shots folder. If I drag the wave file into a project, it sounds fine. Is that an artifact of the audio browser? Some of the snares have similar artifacts as well. When dragged into a project they sound fine.
Is there a setting I'm missing for previewing clips?

Just a guess, but it sounds like something is up with your preview bus. Is it routed to the master bus or directly to the interface? If it goes to the master bus, are there FX on the master bus? Are there FX on the preview bus?
 
It sounds like somethings up there, but It's hard to know what it might be without looking at your project.

gswitz
Just a guess, but it sounds like something is up with your preview bus. Is it routed to the master bus or directly to the interface? If it goes to the master bus, are there FX on the master bus? Are there FX on the preview bus?
 
It sounds like somethings up there, but It's hard to know what it might be without looking at your project.

No, routing is normal. No effects on the preview bus, only a concrete limiter on the master set to -0.1db.
Preview -> Master -> Interface
ProChannel is turned off on the preview bus.
What happens when you preview Kick_015? Does it sound normal?

Try sending preview direct to the interface?

Check your interface to make sure output is at unity.

Does it happen in a new project?

see related post http://forum.cakewalk.com/FindPost/3103894
"Preview At Host Tempo" was enabled