Bob,
Here is what I just did:
1) downloaded installer via the Google drive and installed the JMRI as directed
2) clicked on DecoderPro, PanelPro, and SoundPro - none of them opened
3) reinstalled V4.16. DecoderPro opened normally and every pulldown menu works except any choice under "DecoderPro". Once I click on any of those, the same fatal error message pops up and I have to "Force Quit" to get out of DecoderPro
I am OK for now as I do not have to change any settings and very rarely use WiThrottle. I'll monitor any changes and let me know if you want me to try anything else.
Thanks loads to you guys for working on this.
Fran G.