Been using my Audio-gd 12.1 for quite some time now - but I've been having this problem/issue which occurs on/off. I use the DAC with SPDIF TOSLINK only and almost never use the amp component.
Basically what happens is sometimes the audio will stutter / freeze "zzzzzzzz" - and if playing video or a game, the screen will also freeze at the same time. It only happens a few times a day - but I notice that it comes up most with complex musical passages / intense CPU usage / high I/O on HDDs.
Could it be due to the DAC stuttering because high disk I/O / CPU usage somehow interferes with the SPDIF audio stream? Or - is my DAC faulty?