I followed the instructions on the Microsoft webpage about enabling
null session shares - including the bit that said "reboot the server"! but
it didn't work. Then I changed the logon account from Service to a
local user account with Log on as a Service right - that did the trick.
Thanks for your suggestions.
However I have now switched back to my linux machine and 5.4.0
because I want to have a working system for our party on new year's

Still unable to get 6.0 to run on linux - I get:
linux:/usr/local/slimserver # Can't locate DBI.pm in @INC (@INC
contains: /usr/local/slimserver /usr/local/slimserver/CPAN
BEGIN failed--compilation aborted at
/usr/local/slimserver/Slim/DataStores/DBI/DBIStore.pm line 13.
Compilation failed in require at /usr/local/slimserver/Slim/Music/Info.pm
line 18.