Per the suggestions in another thread about distributing the zfdagent
via NAL (thanks!), I am trying this out.

Big problem so far...NAL simply will not launch on some workstations.
Ultimately, I plan on calling NalExpLd at login to install the
zfdagent, but I can't even manually launch it on several workstations.

as a side-by-side test on a machine from each camp:

Both XP SP2 machines, both with 4.91 SP3 client and all Windows Updates
both with prior ZEN remote agents installed
logged into both as Admin equivilent
logged into Tree as myself, login script processed both places

When I map a drive to the Public dir on my Zen server and try to run
either NalExpLd or Nal, one machine will launch either, while the other
machine does absolutely nothing. No process, no noise, no nothing. I
even logged both with regmon, and the failed one just stops for no
logical reason. Both regmon files look the same (at least the failures
do) up to the point where the one stops going. I have replicated this
on several machines so far, none with an obvious commonality.

I was on Zen 7 SP1, and I have even tried applying HP4 to no avail.

Any ideas?