mixing network mounts/local leads to odd behaviour

Hej!
I'll try to keep it terse:
patch developed on osx 10.2.8, max 4.3.2, jitter, 1.2.3
running on a G5, osx 10.4.6, max runtime 4.5 jitter 1.5.2

It's a case where I'm reading from three ms/samba network mounts (pdp patches capturing and generating effected video to raw dv) and combining that in a mixer, recording with jit.qt.record to disk (with audio generated on the G5 also recorded to disk.

The odd bit:
if I manually load the dv streams from from the mount points (click 'read' select in the finder) I can get three streams running with nearly no latency. However, when I do the following:

sprintf read dynebolic0:/%s-c1-001.dv

for all three mounts, they read and then freeze and sometimes play after 4 seconds or so. I slow it down a few 1000 ms to make sure there are enough frames on disk, but it makes no diff. I can add 10seconds of latency and the files just don't play properly. After about 20-30 seconds of playing, they suddenly stop.

The other method of opening the files works as you'd expect. The only thing I can think of is that interaction with the finder's samba mounts is flakey. ...

The linux boxes are rock solid. I can stream between them to my hearts content.

Any ideas?