ok me. i have your answer...
it was the period buffer not being long enough for the (wimpy-er) sound card on the 2nd pc. it
In the SndO constructor, the inPer default value has always been 64. That's the number of samples in one period of the buffer for the sound card.
Changing it to 128 made both pc soundcards work. Although I'll prefer 64 on my main pc for slightly lower latency.
64 for inPer (period buffer size in samples) was fine for my main pc, but not for the 2nd pc.
so now i gotta make that configurable in the gui. sigh. guis are so haaard.
on with the show.