DME call returns SSORequest() - sso.js error

I'm on Lawson 10.0.3 with Workspace, this plain vanilla DME call to a custom table is returning a SSO error of:

Reason: Invalid at the top level of the document.

This is the DME call

 // Do DME Call to Get Supervisor Code
  var s = portalWnd.DMEPath;
  s += "?PROD="+strPDL;
  s += "&FILE=KRMGRDEPT";
  s += "&FIELD=PROCESS-LEVEL;DEPARTMENT;EFFECT-DATE;STOP-DATE;";
  s += "&INDEX=KMDSET1";
  s += "&KEY=" + vCompNum + "=" + vSuperCode;
  s += "&OUT=CSV&DELIM=~&NOHEADER";

I get the same error making a DME call to a standard table, i.e. employee.  Interestingly, the same DME call in the API builder and within the Add-ins for Excel will return data with no errors.

Does anyone know how to resolve this?