I reinstalled slimserver, and it works again.
But I have had to upgrade to 6.3.1, and firmware 55, vs the firmware 15 I was using before - this matters to me, since version 15 inverts phase, as does my Bolder modded SB3, so short term I have resorted to swapping the + and - leads of my speaker cables, but I will have to sort out that version 15 thing later on.
Thanks for the advice,