I posted in the main bug report thread but just for continuity's sake I'll post here also. I'm using KX (I think p3rv3rt b3ar is also) and with RC3 came the nasty volume bug you describe.
I also have trouble with audio hanging on track switch (requiring restart of CF) and no audio upon resume from hibernation or standby (requiring track skip fwd/back - pause/unpause does not bring audio back).
I've found little support from KX users/developers because their real motivation is to use the kxdriver set for recording and music production applications. My reason for using the kx set is that I can implement DSP filters on my outputs - in particular, I have placed crossover filters on the multiple outputs of my Audigy2zs, so I have dedicated high / mid / subwoofer outputs directly to my amplifiers. Losing kx means I have to add another expensive component to my signal chain.
I have no trouble with any of these issues if I use Roadrunner or any other winamp-based frontend (or other media player for that matter) with kx installed, so it seems a reasonable conclusion that CF is addressing the audio hardware in some non-typical way. But it's obviously not a priority for David (with only a few users overlapping CF and KX) so I suspect there's little hope for any solution in the future.