Help please! Jitter/digital distortion while recording audio

Hey guys
Been putting up with this for the last few days so finally time to sort it out.
I have been getting audio glitches while recording into Cubase.
My current set up is:
Imac 27"
3.4GHz intel core i7
OSX 10.7.4
Memory - 16gB 1333Mhz DDR3
Thunderbolt lacie drive 2tb external
Steinberg UR824 usb interface
(if there is anything else I can put up that will help, please let me know)

Basically throughout recording audio, i’ll get digital clicks, and then looking at the waveform (attached) you can see the audio has been messed up during recording.

I turn off airport while recording, and no other programs are running. I changed the USB cable on the interface to a Lindy usb cable (knowing it probably wasn’t the problem) My system SHOULD be able to handle low buffer rates (I keep it at 64 when recording) plus I don’t have any effects on while recording.

Any suggestions would be appreciated.
Screen Shot 2012-11-21 at 1.01.55 PM.jpg


still dropsouts when your raise the buffer from 64 to 128 or 258?

Don’t know mac but do they also have some energysaving options (turn them off) or some tasks like in windows witch run automatically ? (like checking all devices)?

Greetz Bassbase