Hi,
I've been having problems for a while and finally pinned it down.
On my Tau if I enable the headphone output within a few seconds of playing the usual eigenharp lights go out and the ominous green flashing light comes on.
After referring to the manual I notice this means that the Tau couldn't find EigenD any more, which is odd because EigenD is still running. This seems to be repeatable for me regardless of whatever other sound hardware I have connected.
Please let me know if you need any more information.