Hi Simon,
As Scot suggests, running the "batch" render could be your solution.
If you must use the 3dsmax jobtype, please paste the stdout logging info from
the job, directly above the information that you've already posted. I'm curious
as to know what exactly the jobtype is doing to launch the 3dsmax design app.
You can either post it here, or email it to us at support <at> pipelinefx.com. If
you email it, please mention this forum thread in the email, and provide a brief
but concise Subject and description in the body.
Also, please read the 3dsmax jobtype's README.txt file which has relevant
information, such as "known issues".