Hi, when I got it it was 2003, and the standard disc if I recall went up to Windows 2000. However on the site they have supported up to Windows 7.
It's a magnificent beast though.
Anyway, in S6 playback master is Edirol sd90, sd90 wave out L
Record master is Edirol SD90, SD90 wave in L
Am using ASIO driver with triangular dithering
As I said my gut feeling is windows maybe.
And the x1 has all updates, although s6 obviously no longer supported.
Cheers