Please see the link posted by the above poster. The kext error should not prevent you from doing the install. In other words, you should be able to ignore that.

Line6Miller

While you can ignore it, and the installation will complete, Gearbox refuses to communicate with the X3. I guess it's a Snow Leopard compatibility issue.

As a newbie to the Line 6 and the Mac world, I also experienced the dreaded 'Line6Audio.kext' driver error message.  After a couple hours of mucking around trying to find a solution, I stumbled upon this thread and finally got it working by downloading the beta driver.  What a pain.  C'mon Line 6.  Software is a tool designed to do a job. If the user has to spend too much time working on the tool, then the tool's purpose is defeated.  Make your software as easy to operate as an iPhone and you'll kill the competition.  At the very least, be proactive and notify your customers about your products incompatibility issues. As it stands, it took a new user like me a huge amount of time and effort, only to find that the Line 6 X3 was imcompatable with the current Mac OS.

Thank you,

BJD