I'm in the beginning of the migration from ZfD 4.01 to 6.5, so I just
installed(updated) the management agent on a few workstations. Those
workstations are not imported anymore, and I can't do a remote control
on the with agent 4.01 registered and updated workstaions (Error 1488).

Could it be, that a dash in the treename is the reason for this (ie.
tree-1)? When I look at the import-logfile, the treename is missing
(completely) and the errormessage states that the workstaion cannot be
imported because of missing treename