Same here bro :\
I am getting the same sound jittering.
I am using:
PIII 600Mhz
GF2 GTS 32 DDR
512MB PC133
SB Live!
PJ64 v1.40
I have tried refining many settings and I got it to work very nicely on v1.30 but now with v1.40 I can't get it to work without stuttering sound specially on Z64
Any tips and pointers highly appreciated, Using the other sound plugin just slows down the whole lot. I should be getting a XP 1800+ or higher soon I hope that helps.
Atl.