If you have a very fast machine (such as a P600 or higher) and you’re hearing clicks in the audio stream under R5, you’ve encountered a known bug. Fortunately, there’s also a known fix.
Add the following line to your ~/config/boot/UserSetupEnvironment:

export OVERRIDE_AUDIO_BUFFER_FRAME_COUNT=256

and reboot (yes, reboot — it’s not enough to restart the media_server). The clicking should go away.
If you have a SB 128 PCI or similar card, you also may experience clicking after 12 hours of uptime, even if you don’t have a fast machine. Restarting the media server should fix this.