Board support package was installed from within the Arduino IDE, "Adafruit Bluefruit nRF52 Feather" is selected as board, "0.5.0 dual, S132 2.0.1" is selected as bootloader, appropriate COM port is selected, Debug Mode is set to Level 0 (Release).Sketch uses 20,844 bytes (12%) of program storage space. Maximum is 165,888 bytes.
Global variables use 0 bytes (0%) of dynamic memory, leaving 51,072 bytes for local variables. Maximum is 51,072 bytes.
java.io.IOException: Cannot run program "C:\Users\Brent": CreateProcess error=193, %1 is not a valid Win32 application
at java.lang.ProcessBuilder.start(ProcessBuilder.java:1048)
at processing.app.helpers.ProcessUtils.exec(ProcessUtils.java:26)
at cc.arduino.packages.Uploader.executeUploadCommand(Uploader.java:129)
at cc.arduino.packages.uploaders.SerialUploader.uploadUsingPreferences(SerialUploader.java:207)
at cc.arduino.UploaderUtils.upload(UploaderUtils.java:78)
at processing.app.SketchController.upload(SketchController.java:709)
at processing.app.SketchController.exportApplet(SketchController.java:682)
at processing.app.Editor$DefaultExportHandler.run(Editor.java:2189)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.io.IOException: CreateProcess error=193, %1 is not a valid Win32 application
at java.lang.ProcessImpl.create(Native Method)
at java.lang.ProcessImpl.<init>(ProcessImpl.java:386)
at java.lang.ProcessImpl.start(ProcessImpl.java:137)
at java.lang.ProcessBuilder.start(ProcessBuilder.java:1029)
... 8 more
An error occurred while uploading the sketch
Grounding the DFU pin to force serial programming doesn't affect the upload process. I'm running Windows 10, and as I mentioned earlier I've tried with both Arduino 1.6.13 and 1.8.5. I'm able to successfully load code onto other arduino boards (Uno, Leonardo/Pro Micro). It seems to be nRF52-specific. I'm also unclear on which bootloader version to select, but both seem to behave the same.