I have a Turtle Beach Aureal Vortex 2 (AU8830) installed in my Pentium 3 box (IBM 300PL 6892).
In general the card works well in pure DOS, there is a Dreamblaster attached to it and everything seems to be awesome except of one issue which is driving me crazy.

Classic DOS Navigator (the last Ritlabs build) hangs immediately after showing its banner if au30dos is loaded.
NDN and DN OSP work, though both are crappy, NDN isn't suitable for 80x25 and DN OSP is really buggy.

Could anyone give me an advice on how may I debug/fix this issue?

Thanks!