Hello Zilch I´ve had had a simular problem whith BiaB, but I´ve build a new PC now.
My new wone it´s a I7 whith the 64 Bit XP professional vershen, but I never had problems whith
native instruments Bandstand and now I have the Kopmplet 5 also running at the new wonn.
If you planed to running Kontakt 4 it would leike better and cheeper to bay the Komplet 6 for I think in Germany 499 €.
In my systhem fore GM you remember that I´ve Bandstand fore the VstI player, if I wouled play live to BiaB so I must be
had the installed the Komplete 5 in stand allone too, than can play the B4 II and also athers to the playback simultan!
But I plan to bay the Kore 2 SE to have the brend new soundlibarys und real brass and sax instruments.
I hope I caned help you.

LG Matze

Oh sorry I´f forgotten my soundcard is Delta 1010LT but the 64 Bit vershen from M-Audio is a Beta vershen!

But I´ve never had have problems whith the Soundcard