In case this is useful, here is what the PEMPro Logs show:
0000044 2016-08-10 22:46:48.762: Debug, SgProCam, Sending: http://localhost:59590/json/reply/SgCaptureImage, Params: {"BinningMode":1,"IsoMode":1600,"ExposureLength":15,"Gain":"","Speed":"Normal","FrameType":"Light","Path":"C:\Users\bill\Documents\CCDWare\PEMProV3\SGProImage","UseSubframe":false,"X":0,"Y":0,"Width":0,"Height":0}
0000045 2016-08-10 22:46:48.763: Debug, SgProCam, Response: {"Success":false,"Message":"Invalid ISO option specified!","Receipt":"00000000000000000000000000000000"}
0000046 2016-08-10 22:46:48.763: Error, SgCaptureImage, Invalid ISO option specified!