Give Up?

I'm going to guess the DAC's bit rate was not selected properly to work with the transport's bit rate.

Or, the wrong digital input was selected on the DAC.

Is it a Behringer? I had a similar problem with my Behringer.

Is there a prize? :)

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.