Ok, I was able to resolve my issues.
From a shell, run the commands:
sudo kextcache -system-caches
sudo kextcache -update-volume /
The second command showed me which kext's it didn't like (IOUSBAttachedSCSI in my case). I deleted that kext and re-ran the command, and it completed successfully. Then I ran multibeast again and it worked fine. After a reboot, my Bluetooth and audio worked properly. Hope this helps.