This is a pretty good discussion about how to make sure the convert task is running in the best possible environment:
Basically make sure that if you've updated EPDM that you also updated the task add-in and that you clicked the "Reset" button in the task scripting options (Page 97 of the 2013 install guide). Make sure wherever it runs is a fully supported computer with a supported video card and driver (validate in SolidWorks Rx), and check the log files created by the convert task on the workstation that ran it to see if there are specific errors for that file.
Charley, thank you.
For myself, the task add-in was out of date.
I updated following the instructions here and it is now working correctly.