Prelude 1200 - heavy distortion (and crash) above 27420Hz

[Dandy]

Hi there.

...
but as soon as I go above 27420hz frequency, the sound is distorted (very high pitched garbage / hissing) and the machine crashes soon after.
...
Like I said, playback at 27420hz works fine. But this card can do better, right?

But your ears can't.
 

...
Anything else I should look into?

Yes:
http://en.wikipedia.org/wiki/Audible_range

http://en.wikipedia.org/wiki/Sample_rate

To avoid misunderstandings, you may want to refer to "27420 Hz sample frequency (or sample rate)" instead of "27420hz frequency".

"27420hz frequency" denotes a tone with a frequency of 27420 Hz, which no human being is able to hear (in my best days I could hear frequencies up to 24.500 Hz...).

[Dandy]

...in todays digital world of crap sound.
Makes me glad I have my Tascam reel to reel mastering machine and a decent vinyl collection.

Exactly.
I also still have my 2.5 m vinyl LPs, about 1.5 m vinyl Maxi Singles and roughly 500 vinyl singles from my DJ period (1974 - 1980).