Random blast of 0db white noise.

System is in my office with two Jamo bookshelf speakers, a Klipsch 10" Sub, an old Denon 3802  that has never given me a lick of problem in all the years I used it in the theater room.  Also, an IBM i5 Thinkcenter PC, a Parasound ZDAC, a Parasound ZPhono and a VPI Super Scoutmaster.

Anyway, running JRiver 21 with a few TB of discs I've ripped or downloaded HD FLAC files.  Sounds pretty damn good for being a bunch of second use gear, but occasionally I'll be listening to music or a podcast and I'll get a blast of white noise (could be pink, but I haven't RTA'd it :)), and I have to hit the mute button on the keyboard.  It killed the tweeters on a set of KEF iQ10's, but so far the Jamo's are holding up.  I keep the volume on the Denon at -10 and then control the volume from the keyboard or via whatever player I'm using.  I've never run into anything like this before, and as you can imagine, it's a bit unnerving when it starts blasting.

My gut tells me it's the DAC or the PC, as it happens with different software, and I don't think there is anything wrong with the Denon, and it's old enough to have a minimum of DSP onboard, ie; no Audyssey or such.

Ideas?