Give Up?

Maybe it didn't like your choice of digital cable... or it caught a power-line spike and a chip freaked out in which case unplugging it and plugging it back in could have "fixed" it...

You screwed up?

Sounds like a few possibilities:

DC output from the DAC wreaking havoc.
DAC and transport are not linking up and the amplifier is going in and out of protection mode.

Take out the new DAC, replace with old and see if the problem reoccurs. If it does not, the problem is your new DAC and I would call the dealer you bought it from or the manufacturer and have them troubleshoot the problem.

If you want to call me, I would be more than happy to help you diagnose it.

Good guesses, but not correct yet.
I have the solution/answer and the fix already; I appreciate advice, but the situation is already corrected. I just want to see if anyone can guess what the problem was. Just a fun system "brain teaser" for enjoyment.

So far, no correct guesses. I did not screw up; there was a technical problem.

The prize is the satisfaction of being an audio genius and the endless admiration of the community. (Is that enough?)
:)