The customer has responded with the steps used to reproduce the issue:

1. The user who installs the software is an admin (and local admin ofc). I.o.w.
you do a basic standard succesful installation locally on the harddisk of a
computer. Use default locations for installation folder(s).
2. You log a user with a floating profile on the PC (with a domain logon ofc,
not a local logon). Note that the user is not a local admin but given he ain't
installing anything, just running would think that should be ok.
3. When the user starts the software the following message pops
(translated from Dutch) :
"IcePDF Viewer-directory to save userdata cannot be created:
\\srghvlt-dc01\.icesoft\icepdf-viewer. Changes to the standard configuration
will not be saved."

Note that the location where the software tries to access a folder is actually
the name of the domain-logon server (\\srghvlt-dc01), and not the local user's
folder (C:\Documents and Settings\[username])