Hi,
here a report on the findings so far.
In Windows there exists a security policy:
"Devices: Prevent users from installing printer drivers"
on servers (2003 Server, 2008 Server, ..) this policy is by default
activated, on other systems (XP,...) it is by default deactivated.
if this policy is activated it prevents Acrord32 to see the printers
and therefore to print when the $ZF(...) is called from a remote
terminal or a background process, deactivating this policy seems to
help, at least in some cases.
Why this policy prevents a process from seeing an alredy installed
printer is probably one off the eternal enigmas of Windows. Why it has
an influence even when Cache is running with an administrator account
(the documentation says that it doesn't influence administrators) is
still under investigation.
I'll keep you informed on further findings.