Not sure if you got this worked out yet or not, but I have encountered this three times in the past (twice with one specific customer) and worked with Jim Gilliver for a workaround. Please try using a batch file wrapper to see if that makes things work as expected using the contents below.
BATCH FILE CONTENTS:
C:\Progra~2\Pharos\Bin\adldaplogon.exe %* exit /b 0
Save the batch file in the Pharos\Bin folder, and then set the logon event to use the batch file plugin instead of the EXE directly. If Pharos is stored in a different path, please update accordingly.
This was traced down to permissions problem on the PrintServer (PSPrintSrv).
Running the service as user who has the Run As a Service capability and is also a Doming admin cleared up the problem.