samba 3.0.25 with Windows 7 or Vista

[Learner Study]

Hello experts:

I have been using samba 3.0.25 and it has been giving decent
performance with windows XP or 2003 (about 60MB/s reads). But, I just
tried with vista or windows7 but the perf is pretty bad (down to
8MB/s). I even enabled the Customize->video stream option on
vista/windows7 but no impact.

Any ideas what could be going wrong here? Has someone seen this?

Any pointers - greatly appreciated.

Thanks!